javascript - 如何获取 json 返回数据的长度并运行 for 循环

Question

<分区>

Answer 1

用一个简单的 for ... in 循环:

var obj = {
  7: "8,debbie,23",
  8: "3,doggie,20",
  9: "7,dini,22"
};

for(var x in obj){
  console.log(obj[x]);
}

for in 循环的替代方案可以是:

var obj = {
  7: "8,debbie,23",
  8: "3,doggie,20",
  9: "7,dini,22"
};

Object.keys(obj).forEach(function(key) {
    console.log(key, obj[key]);
});

重要的是要知道，只有当 keys 从 0 开始时，您才能使用接下来的两个选项。

您可以像这样计算对象中的元素:

var obj = {
  0: "8,debbie,23",
  1: "3,doggie,20",
  2: "7,dini,22"
};
var wrong_count = obj.length; //this will return undefined
var correct_length = Object.keys(obj).length; //this will return 3
console.log(wrong_count);
console.log(correct_length);

for(var i = 0; i < correct_length; i++){
  console.log(obj[i]);
}

有关Object.keys()的更多信息，您可以引用link .

另一种替代方法是使用 for in 循环:

var obj = {
  0: "8,debbie,23",
  1: "3,doggie,20",
  2: "7,dini,22"
};

var another_count = 0;
for(var x in obj){
	another_count++;
}
console.log(another_count);

for(var i = 0; i < another_count; i++){
  console.log(obj[i]);
}