(window.webpackJsonp=window.webpackJsonp||[]).push([[1784],{2192:function(t,a,s){"use strict";s.r(a);var e=s(31),n=Object(e.a)({},(function(){var t=this,a=t.$createElement,s=t._self._c||a;return s("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[s("h1",{attrs:{id:"set"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#set"}},[t._v("#")]),t._v(" Set")]),t._v(" "),s("p",[t._v("The Set object lets you store unique values of any type, whether primitive values or object references.")]),t._v(" "),s("p",[t._v("Set objects are collections of values. You can iterate through the elements of a set in insertion order. A value in the Set may only occur "),s("strong",[t._v("ONCE")]),t._v("; it is unique in the Set's collection. Distinct values are discriminated using the "),s("strong",[t._v("SameValueZero")]),t._v(" comparison algorithm.")]),t._v(" "),s("p",[s("a",{attrs:{href:"http://www.ecma-international.org/ecma-262/6.0/#sec-set-objects",target:"_blank",rel:"noopener noreferrer"}},[t._v("Standard Specification About Set"),s("OutboundLink")],1)]),t._v(" "),s("h2",{attrs:{id:"creating-a-set"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#creating-a-set"}},[t._v("#")]),t._v(" Creating a Set")]),t._v(" "),s("p",[t._v("The Set object lets you store unique values of any type, whether primitive values or object references.")]),t._v(" "),s("p",[t._v("You can push items into a set and iterate them similar to a plain JavaScript array, but unlike array, you cannot add a value to a Set if the value already exist in it.")]),t._v(" "),s("p",[t._v("To create a new set:")]),t._v(" "),s("div",{staticClass:"language-js extra-class"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" mySet "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Or you can create a set from any iterable object to give it starting values:")]),t._v(" "),s("div",{staticClass:"language-js extra-class"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" arr "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" mySet "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("arr"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("In the example above the set content would be "),s("code",[t._v("{1, 2, 3, 4, 5}")]),t._v(". Note that the value 4 appears only once, unlike in the original array used to create it.")]),t._v(" "),s("h2",{attrs:{id:"adding-a-value-to-a-set"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#adding-a-value-to-a-set"}},[t._v("#")]),t._v(" Adding a value to a Set")]),t._v(" "),s("p",[t._v("To add a value to a Set, use the "),s("code",[t._v(".add()")]),t._v(" method:")]),t._v(" "),s("div",{staticClass:"language-js extra-class"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("mySet"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("If the value already exist in the set it will not be added again, as Sets 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4}")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"intersection-and-difference-in-sets"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#intersection-and-difference-in-sets"}},[t._v("#")]),t._v(" Intersection and difference in Sets")]),t._v(" "),s("p",[t._v("There are no build-in methods for intersection and difference in Sets, but you can still achieve that but converting them to arrays, filtering, and converting back to Sets:")]),t._v(" "),s("div",{staticClass:"language-js extra-class"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("var")]),t._v(" set1 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token 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"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("Array"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("from")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("set1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("x")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=>")]),t._v(" set2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("has")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("x"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//Set {3, 4}")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" difference "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("Array"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("from")]),s("span",{pre:!0,attrs:{class:"token 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"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//Set {1, 2}")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"iterating-sets"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#iterating-sets"}},[t._v("#")]),t._v(" Iterating Sets")]),t._v(" "),s("p",[t._v("You can use a simple for-of loop to iterate a Set:")]),t._v(" "),s("div",{staticClass:"language-js extra-class"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" mySet "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("for")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" value "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("of")]),t._v(" mySet"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("value"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// logs 1, 2 and 3")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("When iterating over a set, it will always return values in the order they were first added to the set. For example:")]),t._v(" "),s("div",{staticClass:"language-js extra-class"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" set "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("6")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\nset"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\nset"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//5 already exists in the set")]),t._v("\nArray"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("from")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("set"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//[4, 5, 6, 10]")]),t._v("\n\n")])])]),s("p",[t._v("There's also a "),s("code",[t._v(".forEach()")]),t._v(" method, similar to "),s("code",[t._v("Array.prototype.forEach()")]),t._v(". It has two parameters, "),s("code",[t._v("callback")]),t._v(", which will be executed for each element, and optional "),s("code",[t._v("thisArg")]),t._v(", which will be used as "),s("code",[t._v("this")]),t._v(" when executing "),s("code",[t._v("callback")]),t._v(".")]),t._v(" "),s("p",[s("code",[t._v("callback")]),t._v(" has three arguments. The first two arguments are both the current element of Set (for consistency with "),s("code",[t._v("Array.prototype.forEach()")]),t._v(" and "),s("code",[t._v("Map.prototype.forEach()")]),t._v(") and the third argument is the Set itself.")]),t._v(" "),s("div",{staticClass:"language-js extra-class"},[s("pre",{pre:!0,attrs:{class:"language-js"}},[s("code",[t._v("mySet"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("value"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" value2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("set")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=>")]),t._v(" console"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("log")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("value"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// logs 1, 2 and 3")]),t._v("\n\n")])])]),s("h4",{attrs:{id:"syntax"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#syntax"}},[t._v("#")]),t._v(" Syntax")]),t._v(" "),s("ul",[s("li",[t._v("new Set([iterable])")]),t._v(" "),s("li",[t._v("mySet.add(value)")]),t._v(" "),s("li",[t._v("mySet.clear()")]),t._v(" "),s("li",[t._v("mySet.delete(value)")]),t._v(" "),s("li",[t._v("mySet.entries()")]),t._v(" "),s("li",[t._v("mySet.forEach(callback[, thisArg])")]),t._v(" "),s("li",[t._v("mySet.has(value)")]),t._v(" "),s("li",[t._v("mySet.values()")])]),t._v(" "),s("h4",{attrs:{id:"parameters"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#parameters"}},[t._v("#")]),t._v(" Parameters")]),t._v(" "),s("table",[s("thead",[s("tr",[s("th",[t._v("Parameter")]),t._v(" "),s("th",[t._v("Details")])])]),t._v(" "),s("tbody",[s("tr",[s("td",[t._v("iterable")]),t._v(" "),s("td",[t._v("If an iterable object is passed, all of its elements will be added to the new Set. null is treated as undefined.")])]),t._v(" "),s("tr",[s("td",[t._v("value")]),t._v(" "),s("td",[t._v("The value of the element to add to the Set object.")])]),t._v(" "),s("tr",[s("td",[t._v("callback")]),t._v(" "),s("td",[t._v("Function to execute for each element.")])]),t._v(" "),s("tr",[s("td",[t._v("thisArg")]),t._v(" "),s("td",[t._v("Optional. Value to use as this when executing callback.")])])])]),t._v(" "),s("h4",{attrs:{id:"remarks"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#remarks"}},[t._v("#")]),t._v(" Remarks")]),t._v(" "),s("p",[t._v("Because each value in the Set has to be unique, the value equality will be checked and is not based on the same algorithm as the one used in the === operator. Specifically, for Sets, +0 (which is strictly equal to -0) and -0 are different values. However, this has been changed in the latest ECMAScript 6 specification. Starting with Gecko 29.0 (Firefox 29 / Thunderbird 29 / SeaMonkey 2.26) (bug 952870) and a recent nightly Chrome, +0 and -0 are treated as the same value in Set objects. Also, NaN and undefined can also be stored in a Set. NaN is considered the same as NaN (even though NaN !== NaN).")])])}),[],!1,null,null,null);a.default=n.exports}}]);