Describes basic Js Array Operations

This article describes basic methods for Js Array Operations 1. array detection

Var newArr = [1, 2, 3]; newArr instanceof Array; // trueArray. isArray (newArr); // true // Array. isArray (newArr) only supports ie9 +, firefox 4 +, safari 5 +, opera 10.5 +, and chrome

2. Create an array

Var newArr = new Array (); // create an Array var newArr = new Array (3); // create an Array and specify the length var newArr = new Array (1, 2, [3, 4]); // create an array and assign values

3. Add Elements

Var newArr = new Array (); // create an Array var newArr = new Array (3); // create an Array and specify the length var newArr = new Array (1, 2, [3, 4newArr. push ('A'); // 6 newArr; // [1, 2, 3, 4, 5, 'a'] newArr. unshift ('B'); // 7 newArr; // ['B', 1, 2, 3, 4, 5, 'a'] newArr. splice (2, 0, 'C'); // [] newArr; // ["B", 1, "C", 2, 3, 4, 5, "A"]); // creates an array and assigns A value.

4. Delete Elements

var newArr = [1,2,3,4,5];newArr.pop();  //5newArr;  // [1,2,3,4]newArr.shift(); //1newArr;  // [2,3,4]newArr.splice(1,2); //[3,4]newArr;  //[2]

5. truncate and merge elements

var newArr = ['A','B','C','D','E'];newArr.slice(2); //["C", "D", "E"]newArr.slice(1,4); //["B", "C", "D"]newArr.concat('M');  //["A", "B", "C", "D", "E", "M"]

6. Copy an array

var newArr = ['A','B','C','D','E'];newArr.slice(0); //["A", "B", "C", "D", "E"]newArr.concat();  //["A", "B", "C", "D", "E"]

7. Sort Arrays

var newArr = ['A','C','B','D','M'];newArr.reverse();  //["M", "D", "B", "C", "A"]newArr.sort();  //"A", "B", "C", "D", "M"]

8. String Conversion of Arrays

Var newArr = [1, 2, 3]; newArr. join (','); // "1, 2, 3" newArr. toString (); // "1, 2, 3" newArr. toLocaleString (); // "1, 2, 3" newArr. valueOf (); // [, 3] // toLocaleString, toString, valueOf: can be considered as a special use of join, not commonly used

9. Search for Arrays

Var newArr = [1, 2, 3, 4, 5, 4, 3, 2, 3, 4]; newArr. indexOf (3); // the location where element 3 appears for the first time: 2newArr. indexOf (3, 4); // start from position 3 to find the position where element 4 appears for the first time: 6newArr. lastIndexOf (3); // the position where element 3 is last displayed: 8newArr. lastIndexOf (2, 4); // start from position 4 to find the last location where element 2 appears: 1var person = {name: "lili"}, person1 = [{name: "lili"}], person2 = [person]; person1.indexOf (person); // The returned-1 value must be strictly equal, not just the value equal to person2.indexOf (person ); // return 0 // indexOf () from the past to the next query. The value-1 is not found. // lastIndexOf () is found from the next query. The value-1 is not found.

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