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  • JS基础知识(数组)

    1,数组

    var colors = new Array();
    var colors = new Array(20);
    var colors = new Array(“red”, “blue”, “green”);
    var colors = new Array(3); //create an array with three items
    var names = new Array(“Greg”); //create an array with one item, the string “Greg”
    shift:删除原数组第一项,并返回删除元素的值;如果数组为空则返回undefined
    var a = [1,2,3,4,5];
    var b = a.shift(); //a:[2,3,4,5]   b:1
    unshift:将参数添加到原数组开头,并返回数组的长度
    var a = [1,2,3,4,5];
    var b = a.unshift(-2,-1); //a:[-2,-1,1,2,3,4,5]   b:7
    pop:删除原数组最后一项,并返回删除元素的值;如果数组为空则返回undefined
    var a = [1,2,3,4,5];
    var b = a.pop(); //a:[1,2,3,4]   b:5//不用返回的话直接调用就可以了
    push:将参数添加到原数组末尾,并返回数组的长度
    var a = [1,2,3,4,5];
    var b = a.push(6,7); //a:[1,2,3,4,5,6,7]   b:7
    concat:返回一个新数组,是将参数添加到原数组中构成的
    var a = [1,2,3,4,5];
    var b = a.concat(6,7); //a:[1,2,3,4,5]   b:[1,2,3,4,5,6,7]

    放值:

    var colors = [“red”, “blue”, “green”]; //define an array of strings
    alert(colors[0]); //display the first item
    colors[2] = “black”; //change the third item
    colors[3] = “brown”; //add a fourth item
    在最后面加值:
    var colors = [“red”, “blue”, “green”]; //creates an array with three strings
    colors[colors.length] = “black”; //add a color (position 3)
    colors[colors.length] = “brown”; //add another color (position 4)

    注意:

    数组最多能放4,294,967,295个元素

    last-in-fi rst-out (LIFO)结构:
    var colors = new Array(); //create an array
    var count = colors.push(“red”, “green”); //push two items
    alert(count); //2
    count = colors.push(“black”); //push another item on
    alert(count); //3
    var item = colors.pop(); //get the last item
    alert(item); //”black”
    alert(colors.length); //2
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  • 原文地址:https://www.cnblogs.com/killbug/p/3396484.html
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