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punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("person"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("fullName"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// -> "John Hill"')]),t._v("\n\nperson"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("fullName "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Mary Jones"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("person"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("name"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// -> "Mary"')]),t._v("\n\n")])])]),a("h2",{attrs:{id:"dynamic-variable-property-names"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#dynamic-variable-property-names"}},[t._v("#")]),t._v(" Dynamic / variable property names")]),t._v(" "),a("p",[t._v("Sometimes the property name needs to be stored into a variable. In this example, we ask the user what word needs to be looked up, and then provide the result from an object I've named "),a("code",[t._v("dictionary")]),t._v(".")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" dictionary "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    lettuce"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'a veggie'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    banana"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'a fruit'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    tomato"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'it depends on who you ask'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    apple"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'a fruit'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    Apple"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'Steve Jobs rocks!'")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// properties are case-sensitive")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" word "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("prompt")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'What word would you like to look up today?'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" definition "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" dictionary"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("word"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("alert")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("word "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'\\n\\n'")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" definition"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n\n")])])]),a("p",[t._v("Note how we are using "),a("code",[t._v("[]")]),t._v(" bracket notation to look at the variable named "),a("code",[t._v("word")]),t._v("; if we were to use the traditional "),a("code",[t._v(".")]),t._v(" notation, then it would take the value literally, hence:")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[t._v("console"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("dictionary"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("word"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("  "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// doesn't work because word is taken literally and dictionary has no field named `word`")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("dictionary"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("apple"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// it works! because apple is taken literally")]),t._v("\n\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("dictionary"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("word"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// it works! because word is a variable, and the user perfectly typed in one of the words from our dictionary when prompted")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("dictionary"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("apple"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// error! apple is not defined (as a variable)")]),t._v("\n\n")])])]),a("p",[t._v("You could also write literal values with "),a("code",[t._v("[]")]),t._v(" notation by replacing the variable "),a("code",[t._v("word")]),t._v(" with a string "),a("code",[t._v("'apple'")]),t._v(". See [Properties with special characters or reserved words] example.")]),t._v(" "),a("p",[t._v("You can also set dynamic properties with the bracket syntax:")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" property"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),a("span",{pre:!0,attrs:{class:"token string"}},[t._v('"test"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" obj"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("property"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("obj"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("test"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//1")]),t._v("\n\n")])])]),a("p",[t._v("It does the same as:")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" property"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),a("span",{pre:!0,attrs:{class:"token string"}},[t._v('"test"')]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" obj"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nobj"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("property"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("h2",{attrs:{id:"arrays-are-objects"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#arrays-are-objects"}},[t._v("#")]),t._v(" Arrays are Objects")]),t._v(" "),a("blockquote"),t._v(" "),a("p",[a("strong",[t._v("Disclaimer:")]),t._v(" Creating array-like objects is not recommend. However, it is helpful to understand how they work, especially when working with DOM. This will explain why regular array operations don't work on DOM objects returned from many DOM "),a("code",[t._v("document")]),t._v(" functions. (i.e. "),a("code",[t._v("querySelectorAll")]),t._v(", "),a("code",[t._v("form.elements")]),t._v(")")]),t._v(" "),a("p",[t._v("Supposing we created the following object which has some properties you would expect to see in an Array.")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" anObject "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    foo"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'bar'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    length"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'interesting'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'0'")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'zero!'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'1'")]),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'one!'")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("p",[t._v("Then we'll create an array.")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" anArray "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'zero.'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'one.'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("p",[t._v("Now, notice how we can inspect both the object, and the array in the same way.")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[t._v("console"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("anArray"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" anObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// outputs: zero.  zero!")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("anArray"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" anObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// outputs: one.  one!")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("anArray"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("length"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" anObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("length"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// outputs: 2 interesting")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("anArray"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("foo"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" anObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("foo"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// outputs: undefined bar")]),t._v("\n\n")])])]),a("p",[t._v("Since "),a("code",[t._v("anArray")]),t._v(" is actually an object, just like "),a("code",[t._v("anObject")]),t._v(", we can even add custom wordy properties to "),a("code",[t._v("anArray")])]),t._v(" "),a("blockquote"),t._v(" "),a("p",[a("strong",[t._v("Disclaimer:")]),t._v(" Arrays with custom properties are not usually recommended as they can be confusing, but it can be useful in advanced cases where you need the optimized functions of an Array. (i.e. jQuery objects)")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[t._v("anArray"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("foo "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'it works!'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("anArray"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("foo"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("p",[t._v("We can even make "),a("code",[t._v("anObject")]),t._v(" to be an array-like object by adding a "),a("code",[t._v("length")]),t._v(".")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[t._v("anObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("length "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),a("p",[t._v("Then you can use the C-style "),a("code",[t._v("for")]),t._v(" loop to iterate over "),a("code",[t._v("anObject")]),t._v(" just as if it were an Array. See "),a("a",{attrs:{href:"http://stackoverflow.com/documentation/javascript/187/arrays/852/iteration",target:"_blank",rel:"noopener noreferrer"}},[t._v("Array Iteration"),a("OutboundLink")],1)]),t._v(" "),a("p",[t._v("Note that "),a("code",[t._v("anObject")]),t._v(" is only an "),a("strong",[t._v("array-like")]),t._v(" object. (also known as a List) It is not a true Array. This is important, because functions like "),a("code",[t._v("push")]),t._v(" and "),a("code",[t._v("forEach")]),t._v(" (or any convenience function found in "),a("code",[t._v("Array.prototype")]),t._v(") will not work by default on array-like objects.")]),t._v(" "),a("p",[t._v("Many of the DOM "),a("code",[t._v("document")]),t._v(" functions will return a List (i.e. "),a("code",[t._v("querySelectorAll")]),t._v(", "),a("code",[t._v("form.elements")]),t._v(") which is similar to the array-like "),a("code",[t._v("anObject")]),t._v(" we created above.  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Those different methods will be discussed deeply below.")]),t._v(" "),a("h3",{attrs:{id:"methods-of-retrieving-properties"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#methods-of-retrieving-properties"}},[t._v("#")]),t._v(" "),a("strong",[t._v("Methods of retrieving properties :")])]),t._v(" "),a("p",[t._v("Properties from an object could be retrieved by the following methods,")]),t._v(" "),a("li",[t._v("\n[`for..in`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/for...in) loop\nThis loop is very useful in retrieving enumerable properties from an object.  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The function return will be used as the value of the property.")]),t._v(" "),a("li",[a("code",[t._v("set")]),t._v(" is a function which serves as a setter for the property, or "),a("code",[t._v("undefined")]),t._v(" if there is no setter. The function will receive as only argument the new value being assigned to the property.")])]),t._v(" "),a("p",[a("code",[t._v("value")]),t._v(":")]),t._v(" "),a("ul",[a("li",[t._v("This key defaults to "),a("code",[t._v("undefined")]),t._v(".")]),t._v(" "),a("li",[t._v("The value associated with the property. 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//3\n\nobj.propertyName2 = 3; //and this will be logged every time propertyName2's value is tried to be set\nconsole.log(obj.propertyName2); //this will be logged every time propertyName2 is accessed to get its value \n\n")])])]),a("h2",{attrs:{id:"object-getownpropertydescriptor"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#object-getownpropertydescriptor"}},[t._v("#")]),t._v(" Object.getOwnPropertyDescriptor")]),t._v(" "),a("p",[t._v("Get the description of an specific property in an object.")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[a("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" sampleObject "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    hello"),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'world'")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\nObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("getOwnPropertyDescriptor")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("sampleObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'hello'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),a("span",{pre:!0,attrs:{class:"token comment"}},[t._v('// Object {value: "world", writable: true, enumerable: true, configurable: true}')]),t._v("\n\n")])])]),a("h2",{attrs:{id:"properties-with-special-characters-or-reserved-words"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#properties-with-special-characters-or-reserved-words"}},[t._v("#")]),t._v(" Properties with special characters or reserved words")]),t._v(" "),a("p",[t._v("While object property notation is usually written as "),a("code",[t._v("myObject.property")]),t._v(", this will only allow characters that are normally found in "),a("a",{attrs:{href:"http://stackoverflow.com/questions/1661197/what-characters-are-valid-for-javascript-variable-names",target:"_blank",rel:"noopener noreferrer"}},[t._v("JavaScript variable names"),a("OutboundLink")],1),t._v(", which is mainly letters, numbers and underscore ("),a("code",[t._v("_")]),t._v(").")]),t._v(" "),a("p",[t._v("If you need special characters, such as space, ☺, or user-provided content, this is possible using "),a("code",[t._v("[]")]),t._v(" bracket notation.")]),t._v(" "),a("div",{staticClass:"language-js extra-class"},[a("pre",{pre:!0,attrs:{class:"language-js"}},[a("code",[t._v("myObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'special property ☺'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'it works!'")]),t._v("\nconsole"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),a("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("myObject"),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),a("span",{pre:!0,attrs:{class:"token string"}},[t._v("'special property ☺'")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),a("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n\n")])])]),a("h3",{attrs:{id:"all-digit-properties"}},[a("a",{staticClass:"header-anchor",attrs:{href:"#all-digit-properties"}},[t._v("#")]),t._v(" All-digit properties:")]),t._v(" "),a("p",[t._v("In addition to special characters, property names that are all-digits will require bracket notation. 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