您可以使用for…访问对象的嵌套财产。。。in和forEach循环。

对于在：

for (const key in info) {
    console.log(info[key]);
}

对于每个：

Object.keys(info).forEach(function(prop) {
    console.log(info[prop]);
    // cities: Array[3], continent: "North America", images: Array[3], name: "Canada"
    // "prop" is the property name
    // "data[prop]" is the property value
});

如果您的环境支持ES2017，那么我将推荐Object.entries：

Object.entries(obj).forEach(([key, value]) => {
  console.log(`${key} ${value}`);
});

如Mozillas Object.entries（）文档所示：

Object.entries（）方法返回给定对象自身的数组可枚举属性[key，value]对，顺序与由…提供。。。in循环（区别在于for in循环还列举了原型链中的财产）。

基本上，使用Object.entries，我们可以放弃旧的for。。。循环中：

// This step is not necessary with Object.entries
if (object.hasOwnProperty(property)) {
  // do stuff
}

if (typeof obj === 'object' && obj !== null) {
    Object.keys(obj).forEach(key => {
        console.log("\n" + key + ": " + obj[key]);
    });
}

// *** Explanation line by line ***

// Explaining the bellow line
// It checks if obj is neither null nor undefined, which means it's safe to get its keys. 
// Otherwise it will give you a "TypeError: Cannot convert undefined or null to object" if obj is null or undefined.
// NOTE 1: You can use Object.hasOwnProperty() instead of Object.keys(obj).length
// NOTE 2: No need to check if obj is an array because it will work just fine.
// NOTE 3: No need to check if obj is a string because it will not pass the 'if typeof obj is Object' statement.
// NOTE 4: No need to check if Obj is undefined because it will not pass the 'if type obj is Object' statement either.
if (typeof obj === 'object' && obj !== null) {

    // Explaining the bellow line
    // Just like in the previous line, this returns an array with
    // all keys in obj (because if code execution got here, it means 
    // obj has keys.) 
    // Then just invoke built-in javascript forEach() to loop
    // over each key in returned array and calls a call back function 
    // on each array element (key), using ES6 arrow function (=>)
    // Or you can just use a normal function ((key) { blah blah }).
    Object.keys(obj).forEach(key => {

        // The bellow line prints out all keys with their 
        // respective value in obj.
        // key comes from the returned array in Object.keys(obj)
        // obj[key] returns the value of key in obj
        console.log("\n" + key + ": " + obj[key]);
    });
}

jquery允许您立即执行以下操作：

$.each( obj, function( key, value ) {
  alert( key + ": " + value );
});

为何在循环中，它创建了一个新变量（varsomeVariable），然后将给定对象的每个属性逐一存储在这个新变量（someVariable）中。因此，如果使用块｛｝，则可以进行迭代。考虑以下示例。

var obj = {
     name:'raman',
     hobby:'coding',
     planet:'earth'
     };

for(var someVariable in obj) {
  //do nothing..
}

console.log(someVariable); // outputs planet

这是为了。。。in语句（MDN、ECMAScript规范）。

您可以将其读为“对于obj对象中的每个属性，依次将每个属性分配给PROPT变量”。