另一种选择：

var testObj = {test: true, test1: false};
for(let x of Object.keys(testObj)){
    console.log(x);
}

有很多方法可以遍历对象。请查看以下示例。

var obj = {'name':'John Doe','email':'johndoe@example.com'}

方法1

var keys = Object.keys(obj)
for(var i= 0; i < keys.length;i++){
  console.log(keys[i]+ ': ' + obj[keys[i]])
}

方法2

for(var key in obj){
  console.log(key+': '+ obj[key])
}

方法3

Object.keys(obj).forEach(function (key) {
  console.log(key+ ': ' + obj[key])
})

var validation_messages = {
    "key_1": {
        "your_name": "jimmy",
        "your_msg": "hello world"
    },
    "key_2": {
        "your_name": "billy",
        "your_msg": "foo equals bar"
    }
}
for (var i in validation_messages) {
    console.log("i = \"" + i + "\"");
    console.log("validation_messages[\"" + i + "\"] = ");
    console.log(validation_messages[i]);
    console.log("\n");
    for (var j in validation_messages[i]) {
        console.log("j = \"" + j + "\"");
        console.log("validation_messages[\"" + i + "\"][\"" + j + "\"] = \"" + validation_messages[i][j] + "\"");
        console.log("\n");
    }
    console.log('\n');
}

输出：

i = "key_1"
validation_messages["key_1"] = 
{
  your_name:"jimmy",
  your_msg:"hello world"
}

j = "your_name"
validation_messages["key_1"]["your_name"] = "jimmy"

j = "your_msg"
validation_messages["key_1"]["your_msg"] = "hello world"


i = "key_2"
validation_messages["key_2"] = 
{
  your_name:"billy",
  your_msg:"foo equals bar"
}

j = "your_name"
validation_messages["key_2"]["your_name"] = "billy"

j = "your_msg"
validation_messages["key_2"]["your_msg"] = "foo equals bar"

AgileJon答案的优化和改进版本：

var key, obj, prop, owns = Object.prototype.hasOwnProperty;

for (key in validation_messages ) {

    if (owns.call(validation_messages, key)) {

        obj = validation_messages[key];

        for (prop in obj ) {

            // Using obj.hasOwnProperty might cause you headache if there is
            // obj.hasOwnProperty = function(){return false;}
            // but 'owns' will always work
            if (owns.call(obj, prop)) {
                console.log(prop, "=", obj[prop]);
            }
        }
    }
}

如果使用递归，则可以返回任意深度的对象财产-

function lookdeep(object){
    var collection= [], index= 0, next, item;
    for(item in object){
        if(object.hasOwnProperty(item)){
            next= object[item];
            if(typeof next== 'object' && next!= null){
                collection[index++]= item +
                ':{ '+ lookdeep(next).join(', ')+'}';
            }
            else collection[index++]= [item+':'+String(next)];
        }
    }
    return collection;
}

//example

var O={
    a:1, b:2, c:{
        c1:3, c2:4, c3:{
            t:true, f:false
        }
    },
    d:11
};
var lookdeepSample= 'O={'+ lookdeep(O).join(',\n')+'}';


/*  returned value: (String)
O={
    a:1, 
    b:2, 
    c:{
        c1:3, c2:4, c3:{
            t:true, f:false
        }
    },
    d:11
}

*/

2020年，您需要不可变的通用函数

这将遍历由子对象、数组和字符串组成的多维对象，并应用自定义函数：

export const iterate = (object, func) => {
  const entries = Object.entries(object).map(([key, value]) =>
    Array.isArray(value)
      ? [key, value.map(e => iterate(e, func))]
      : typeof value === 'object'
      ? [key, iterate(value, func)]
      : [key, func(value)]
  );
  return Object.fromEntries(entries);
};

用法：

const r = iterate(data, e=>'converted_'+e);
console.log(r);