1. for循环
var arr = ["first",8];for(var i = 0; i < arr.length;i++){console.log(arr[i]);}first8
2.for… in
var arr = ["first","second",'third' ,"fourth",3,5,8];for(var i in arr){console.log(arr[i] +'/' + i);}//输出结果为：first/0second/1third/2fourth/33/45/58/6
3.for…of
var arr = ["first","second",'third' ,"fourth",3,5,8];for(var item of arr){console.log(item);}//输出结果：firstsecondthirdfourth358
4.foreach方法：被传递给foreach的函数会在数组的每个元素上执行一次，元素作为参数传递给该函数，（不能遍历伪数组）
var arr = ["first","second","third","fourth",3,5,8];//element 表示arr的单元项，index 表示arr单元项对应的索引值arr.forEach(function(element,index){console.log(element + '/' + index);})//输出结果：first/0second/1third/2fourth/33/45/58/6
5.map 遍历数组，并通过callback对数组元素进行操作，并将所有操作结果放入数组中并返回该数组（不能遍历伪数组）
var arr = ["first","second",'third' ,"fourth"];var arr2 = arr.map(function(item){return item.toUpperCase()+1;//map可以返回处理过 的数据})console.log(arr2);//输出Array(4) [ "FIRST1", "SECOND1", "THIRD1", "FOURTH1" ]
6.filter( )返回一个包含所有在回调函数上返回为true的元素新数组，回调函数在此担任的是过滤器的角色，当元素符和条件，过滤器就返回true,而filter则会返回所有符合过滤条件的元素
var arr = ["first","second",'third' ,"fourth",3,5,8];var arr3 = arr.filter(function(item){if(typeof item == 'number'){return item;}})console.log(arr3);//输出Array(3) [ 3, 5, 8 ]
7. every() 当数组中的每一个元素在callback上被返回true时就返回true(注意：要求每一个单元项都返回true时才为true)
every()与filter()的区别是：后者会返回所有符合过滤条件的元素；前者会判断是不是数组中的所有元素都符合条件，并且返回的是布尔值
var arr = ["first","second",'third' ,"fourth",3,5,8];var bol = arr.every(function(element){if(typeof element == 'string'){return element;}})console.log(bol); //false
8.some()只要数组中有一项在callback上就返回true
every()与some()的区别是：前者要求所有元素都符合条件才返回true,后者要求只要有符合条件的就返回true
var arr = ["first","second",'third' ,"fourth",3,5,8];var bol = arr.some(function(element){if(typeof element == 'string'){return element;}})console.log(bol); //true
