add JS array methods markdown cheatsheet

cheatsnake · cheatsnake · commit 2d4495f668f3 · 2021-12-27T20:47:34.000+03:00
diff --git a/JavaScript/Array methods/js-array-methods.md b/JavaScript/Array methods/js-array-methods.md
@@ -0,0 +1,67 @@
+# Array methods cheatsheet
+
+## Adding/Removing elements
+
+-   push(...items) <br>
+    add elements to the end
+
+```js
+const arr = [1, 2, 3];
+arr.push(4);
+// arr = [1, 2, 3, 4]
+```
+
+-   pop() <br>
+    extracts an element from the end
+
+```js
+const arr = [1, 2, 3];
+arr.pop();
+// arr = [1, 2]
+```
+
+-   unshift(...items) <br>
+    add items to the beginning (bad for performance)
+
+```js
+const arr = [1, 2, 3];
+arr.unshift(0);
+// arr = [0, 1, 2, 3]
+```
+
+-   shift() <br>
+    extracts from the beginning
+
+```js
+const arr = [1, 2, 3];
+arr.shift();
+// arr = [2, 3]
+```
+
+-   concat(...items) <br>
+    returns a new array: copy of the current array + `items`
+
+```js
+const arr = [1, 2, 3];
+const newArr = arr.concat(4, 5);
+const newArr2 = newArr.concat([6, 7]);
+// newArr2 = [1, 2, 3, 4, 5, 6, 7]
+```
+
+-   splice(pos, count, ...items) <br>
+    at index `pos` deletes `count` elements and inserts `items`
+
+```js
+const arr = ["a", "*", "*", "d"];
+arr.splice(1, 2, "b", "c");
+// arr = ['a', 'b', 'c', d']
+```
+
+-   slice(start, end) <br>
+    creates a new array, copies elements from index `start` till `end` (not inclusive) into it
+
+```js
+const arr = [1, 2, 3, 4, 5];
+const newArr = arr.slice(1, 4);
+// newArr = [2, 3, 4]
+```
