non1 遍历

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

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

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

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

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

<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>

<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>