for 循环和 for/in 循环的区别
for - 循环代码块一定的次数
for/in - 遍历数组或者对象的属性(对数组或者对象的属性进行循环操作)
注意:for/in 循环会访问该对象的原型,应该用在非数组对象的遍历上,不建议使用该方法遍历数组。
示例:
1 <!DOCTYPE html> 2 <html lang="en"> 3 <head> 4 <meta charset="UTF-8"> 5 <title>Title</title> 6 </head> 7 <body> 8 <script> 9 var myCars = new Array() 10 myCars[0] = "Saab" 11 myCars[1] = "Volvo" 12 myCars[2] = "BMW" 13 Array.prototype.newObject = 1234; 14 Array.prototype.newfunction = function () { console.log("new function");} 15 console.info("数组长度:") 16 console.log(myCars.length) 17 console.info("for 循环") 18 for(var i=0;i<myCars.length;i++){ 19 console.log(myCars[i]) 20 } 21 console.info("for in 循环") 22 for (var x in myCars) 23 { 24 console.log(myCars[x]) 25 } 26 console.info("for of 循环(ES6)") 27 for (var k of myCars) 28 { 29 console.log(k) 30 } 31 </script> 32 </body> 33 </html>
结果: