


Summary of usage examples of javascript array operations (including deletion, addition, interception, merging, etc.)
POP Delete the last item
Delete the last item and return the value of the deleted element; if the array is empty, return undefine
var a = [1,2,3,4,5]; a.pop();//a:[1, 2, 3, 4] a.pop();//a:[1, 2, 3] a.pop();//a:[1, 2]
shift Delete the first item
Delete the first item of the original array and return the value of the deleted element; if the array is empty, return undefine
var a = [1,2,3,4,5]; a.shift(); //a:[2,3,4,5] a.shift(); //a:[3, 4, 5]
push increases to the last
and returns the new array length;
var a = [1,2,3,4,5]; a.push(6);//[1, 2, 3, 4, 5, 6] aa.push('xx');//[1, 2, 3, 4, 5, 6, "xx"] 返回长度7 a.push('yy');//[1, 2, 3, 4, 5, 6, "xx", "yy"] 返回长度8
unshift increases to the front
and returns the new array length;
var a = [1,2,3,4,5]; a.unshift();//[1, 2, 3, 4, 5] a.unshift("cc");//["cc", 1, 2, 3, 4, 5] 返回长度6 a.unshift("aaa");//["aaa", "cc", 1, 2, 3, 4, 5] 返回长度7
reverse array flip
And return the flipped original array, the original array is flipped
var a = [1,2,3,4,5]; a.reverse()//a:[5, 4, 3, 2, 1] 返回[5, 4, 3, 2, 1]
join array into string
And return the string, the original array is changed to
var a = [1,2,3,4,5]; var b=a.join('||');//b:"1||2||3||4||5" a:[1,2,3,4,5]
indexOf array element index
And return the element index. If it does not exist, -1 is returned. The index starts from 0
var a = ['a','b','c','d','e']; a.indexOf('a');//0 a.indexOf(a);//-1 a.indexOf('f');//-1 a.indexOf('e');//4
slice intercepts (slices) the array to get the intercepted array
Returns a new array composed of items from the specified start index (inclusive) to the end index (exclusive) in the original array. The original array is mutated and the index starts from 0
var a = ['a','b','c','d','e']; a.slice(1,3);//["b", "c"] a:['a','b','c','d','e'] a.slice(0,4);//["a", "b", "c", "d"] a.slice(3,4);//["d"]
Splice splicing array The original array changes can be deleted before shift, deleted after pop, and added before unshift, which has the same effect as adding after push
Return the spliced element array, the original array changes, and the index starts from 0
/*参数是2个*/ //第一参数是索引(从0开始),第二是长度 var a = ['a','b','c','d','e']; a.splice(0,2);//["a", "b"] a:["c", "d", "e"] a.splice(0,2);//["c", "d"] a:["e"] var a = ['a','b','c','d','e']; a.splice(0,1);//["a"] a:["b", "c", "d", "e"] 同shift前删除 var a = ['a','b','c','d','e'] a.splice(a.length-1,1)l//["e"] a:["a", "b", "c", "d"] 同pop前删除 /*参数大于2个*/ //splice(start,deleteCount,val1,val2,...):从start位置开始删除deleteCount项,并从该位置起插入val1,val2,... var a = ['a','b','c','d','e']; a.splice(3,1,10,21,238,99);//["d"] a:["a", "b", "c", 10, 21, 238, 99, "e"] var a = ['a','b','c','d','e']; a.splice(a.length,100000000,88)//返回 [] 从最后元素后面的元素,截取长度任意个,肯定是空 a:["a", "b", "c", "d", "e", 88] 同push后增加 var a = ['a','b','c','d','e']; a.splice(a.length,0,88)//返回 [] 从最后元素后面的元素,截取长度任意个,肯定是空 a:["a", "b", "c", "d", "e", 88] 同push后增加 var a = ['a','b','c','d','e']; a.splice(0,0,88,99)//返回 [] 从第一个元素,截取长度0个 肯定是空 a:[88, 99, "a", "b", "c", "d", "e"] 同unshift前增加
concat array merge
Return the new array after merging, the original array will be changed
var a = ['a','b','c','d','e']; a.concat([88,99]);//["a", "b", "c", "d", "e", 88, 99] a:["a", "b", "c", "d", "e"] var b= [9999,10000] a.concat(b);// ["a", "b", "c", "d", "e", 9999, 10000] a:["a", "b", "c", "d", "e"]
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