5个数组方法

1.Array.forEach()  遍历数组 无需return

var animals = [‘dog‘, ‘cat‘, ‘mouse‘];

animals.forEach(function(item){
    console.log(item);
});

2.Array.map()  遍历数组 并生成新的数组

var numbers = [2, 4, 6, 8];

var doubleNums = numbers.map(function(element) {
    return element * 2;
});

console.log(‘doubleNums: ‘, doubleNums)

3.Array.filter() 筛选数组成员

var scores = [3, 12, 5, 23, 19, 7];

var topScores = scores.filter(function(item){
    if (item > 10){
        return true;
    } else {
        return false;
    }
});

console.log(‘topScores: ‘, topScores);

4.Array.indexOf() 获取数组中某个元素的索引值(不存在 值未 -1)

var a = [2, 9, 9, 18];

var i = a.indexOf(9);

console.log(‘i: ‘, i);

5.Array.every() 匹配数组中的每个元素 是否符合条件

var ages = [23, 19, 32, 44];

var olderThan18 = ages.every(function(element) {
    return element > 18;
});

console.log(‘olderThan18: ‘, olderThan18);