Methods of array arrays in JavaScript

Find: IndexOf, lastIndexOf

Iterations: Every, filter, ForEach, map, Somereduce, Reduceright

Usage:

1 /*2 1 Find a method:3 * Arr.indexof (value)4 * One parameter returns the position subscript of the array where value is located5 * Return when not found-16  * 7 * Arr.indexof (start, value)8 * Find value from start to return subscript9 * Return when not found-1Ten  *  One * Arr.lastindexof (value) A * return to subscript from the rear -  *  -  *  the  *  - * * Iteration method: - * Arr.every (function (item, index, arr) { - * Return item > 2; Returns true if each item is greater than 2 otherwise false +  * })  - * An incoming function executes a function on each item, + * Returns TRUE if each entry returns True A * If there is a return false, then the return is false. at  *  - * Arr.filter (function (item, index, arr) { - * Return item > 2; Returns an array element that is greater than 2 -  * } )  - * Pass in a function for each element to execute - * The result is true and the element returns in  *          - * Arr.foreach (function (item, index, arr) { to * Alert (item) +  * }) - * Provides a loop method the * Each element performs a function *  *  $ * ARR.MAP (function (item, index, arr) {Panax Notoginseng * Return item * 2; -  * }) the * Performs a function on each item of ARR and returns the result of execution +  *  A  *  the * Arr.some (function (Item,index,arr) { +  *      - * RETRN item > 2; $  * }) $ * to judge each element in Arr, - * There is a return true and finally returns True - * If all is false, then return false the  *  -  * Wuyi  *  the * Arr.reduce (function (prev, cur, index, array) { - *//Money A value current value index position array Wu * return prev + cur; -  * }) About * Each element in the array is added and finally returned $  *  -  *  -  *  - * Arr.reduceright () A * The array is executed from right to left to return the final result +  *  the  *  -  *  $  *  the  *  the  *  the  *  the  *  -  * */

Add: Push, pop, shift, Unshift

Intercept Splice, Slice

Action: concat, join, reverse, sort

Usage:

1 //how arrays are created2 //1 Not recommended3 //var arr = new Array ();4 //2 recommended JS array internal data types can be different5 vararr = [1,2,3,4,true, "ABC",NewDate ()];6 //alert (arr.length);7 //JS Array can arbitrarily change the length of the element type arbitrary8Arr.length = 5;9 alert (arr);Ten  One /* A * Common methods for arrays - * 1 Array Add delete element - * result = Arr.push (Value1,value2,value3,....) adds an element to an array returns the value of the new array's length the * result = Arr.pop () returns the element at the tail of the array and removes -  *      - * result = Arr.shift () removes an element from the head and returns the head element - * result = Arr.unshift (A,b,c,d,e ...) Insert some elements from the head returns the new array length +  *  - * 2 Array intercept + * Arr.splice (1,2,3,4,5) A * Methods for intercepting arrays: Changing the array itself at * The first parameter indicates the starting position - * The second parameter indicates the number of items to intercept - * After the third parameter, as a subarray, the array is inserted from the intercepted position - * Arr.splice (1) 1 after the elements are all cut off - * Arr.splice Two elements starting from the 1th subscript element -  *  in  *   - * result = Arr.slice (2,3) to * Intercept operation the first parameter is the starting point of interception, the second parameter is the end left closed right open intercept + * Returns the intercepted result without changing the array itself -  *  the  *  * * 3 Array operation method $  *  Panax Notoginseng * result = Arr1.concat (ARR2) - * arr1 and arr2 are stitched back the * Do not change the array itself +  *   A * result = Arr.join ("-") the * Add a-symbol between each element and return +  *  - * Arr.reverse () reverse array order $ * Change the array itself $  *  - * Arr.sort () positive order - * But compare each value by one byte of the string the * For example, 10 and 4 compare, will think 1:4 small 10 will be ranked in front - * Change the array itselfWuyi * If you want the correct sort you need to write a method to pass in sort () the * For example - * Function Compare (value1, value2) { Wu * if (value1 < value2) { - * RETURN-1; About *}else if (value1 > value2) { $ * return 1; - *}else{ - * return 0; -  *         }     A  *     } + * Then call Arr.sort (Compare) the * So we can sort the normal sequence we want . -  *  $  * */

Methods of array arrays in JavaScript