【遍历】

• 如何在Array.forEach的循环里break
• 【underscore.js 源码解读】for ... in 存在的浏览器兼容问题你造吗

1. 数组

1.1 for i++

var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
for (var i = 0, l = arr.length; i < l; i++) {
    console.log(i, arr[i])
}

 输出：

1.2 for l-- 

var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
for (var l = arr.length; l--;) {
    console.log(l, arr[l])
}

输出： 

应用： 

var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
for (var l = arr.length; l--;) {
    arr.splice(l, 1)
}
console.log(arr) // []

1.3 while l--

var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
var l = arr.length
while(l--) {
    console.log(l, arr[l])
}

输出： 

2.对象

var obj = {one: 1, two: 2, three: 3}
for (var key in obj) {
    console.log(key, obj[key])
}

输出：

3. ES5

var arr = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
arr.forEach(function(value, index, array) {
    console.log(index, value, array)
})

 输出：

4. Underscore.js

<script src="underscore.js"></script>
<script>
    var list = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
    _.each(list, function(element, index, list) {
        console.log(element, index, list, this)
    }, list)


    _.each({one: 1, two: 2, three: 3}, function(value, key, list) {
        console.log(value, key, list)
    })
</script>

输出：

5. jQuery

<script src="jquery-1.10.2.js"></script>
<script>
    var list = ['a', 'b', 'c', 'd', 'e', 'f', 'g']
    $.each(list, function(index, value) {
        console.log(index, value)
    })


    $.each({one: 1, two: 2, three: 3}, function(key, value) {
        console.log(key, value)
    })
</script>

输出：

6.Angular

angular.forEach(['a', 'b'], function(value, index) {
    console.log(value, index)
})

angular.forEach({a: 1, b: 2}, function(value, key) {
    console.log(value, key)
})

7.Python

python list遍历

info = ['a','b','c','d','ee','fff']
for m in info:
    print m

for in

for in 循环

Object.prototype.bar = 1
var foo = {goo: undefined}
for (var p in foo) {
    console.log(p) // goo bar
    if (foo.hasOwnProperty(p)) {
        console.log('hasOwnProperty', p) // goo
    }
}