for循环
var x = 0;
var i;
for (i=1; i<=10000; i++) {
x = x + i;
}
x; // 50005000
遍历数组
var arr = ['Apple', 'Google', 'Microsoft'];
var i, x;
for (i=0; i<arr.length; i++) {
x = arr[i];
alert(x);
}
退出循环 break
for ... in
把一个对象的所有属性依次循环出来
var o = {
name: 'Jack',
age: 20,
city: 'Beijing'
};
for (var key in o) {
alert(key); // 'name', 'age', 'city'
}
var o = {
name: 'Jack',
age: 20,
city: 'Beijing'
};
for (var key in o) {
if (o.hasOwnProperty(key)) {
alert(key); // 'name', 'age', 'city'
}
}
for ... in对Array的循环得到的是String而不是Number
var a = ['A', 'B', 'C'];
for (var i in a) {
alert(i); // '0', '1', '2'
alert(a[i]); // 'A', 'B', 'C'
}
练习
'use strict';
var arr = ['Bart', 'Lisa', 'Adam'];
for(var i in arr)
{
alert('Hello,'+arr[i]+"!");
}
