JAVASCRIPT

[ Solved – 10 Answers ] JAVASCRIPT – How to Loop through plain JavaScript object with objects as members

  • How to loop through all members in a JavaScript object including values that are objects.
  • For example, how could you loop through this (accessing the “your_name” and “your_message” for each)?
Javascript Code
var validation_messages = {
    "key_1": {
        "your_name": "jimmy",
        "your_msg": "hello world"
    },
    "key_2": {
        "your_name": "billy",
        "your_msg": "foo equals bar"
    }
}

Javascript Code
for (var key in validation_messages) {
    // skip loop if the property is from prototype
    if (!validation_messages.hasOwnProperty(key)) continue;

    var obj = validation_messages[key];
    for (var prop in obj) {
        // skip loop if the property is from prototype
        if(!obj.hasOwnProperty(prop)) continue;

        // your code
        alert(prop + " = " + obj[prop]);
    }
}

  • Under ECMAScript 5, we can combine Object.keys() and Array.prototype.forEach():
Javascript Code
var obj = {
    first: "John", 
    last: "Doe"
};

//
//  Visit non-inherited enumerable keys
//
Object.keys(obj).forEach(function(key) {

    console.log(key, obj[key]);

});

  • The problem with this
Javascript Code
for (var key in validation_messages) {
   var obj = validation_messages[key];
   for (var prop in obj) {
      alert(prop + " = " + obj[prop]);
   }
}

is that we also loop through the primitive object’s prototype.

With this one we will avoid it:

Javascript Code
for (var key in validation_messages) {
   if (validation_messages.hasOwnProperty(key)) {
      var obj = validation_messages[key];
      for (var prop in obj) {
         if (obj.hasOwnProperty(prop)) {
            alert(prop + " = " + obj[prop]);
         }
      }
   }
}

  • To Using Underscore.js’s _.each:
Javascript Code
_.each(validation_messages, function(value, key){
    _.each(value, function(value, key){
        console.log(value);
    });
});

Javascript Code
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;
}
Javascript Code
//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
}

*/

Javascript Code
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]);
            }

        }

    }

}

Javascript Code
for(var k in validation_messages) {
    var o = validation_messages[k];
    do_something_with(o.your_name);
    do_something_else_with(o.your_msg);
}

Javascript Code
for(var key in validation_messages){
    for(var subkey in validation_messages[key]){
        //code here
        //subkey being value, key being 'yourname' / 'yourmsg'
    }
}

  • For this object:
Javascript Code
var myObj = {
    pageURL    : "BLAH",
    emailBox   : {model:"emailAddress", selector:"#emailAddress"},
    passwordBox: {model:"password"    , selector:"#password"}
};

code:

Javascript Code
 var myregex = /^[0-9]*$/;
            if (myregex.exec(prop) != prop) {
                thisYes = true;
                variableList.push({item:thisVar + "." + prop,value:obj[prop]});
            }
          }
          if ( ! thisYes )
            variableList.push({item:thisVar,value:obj});
       }
    }
    return variableList;
}

// Get the object items into a simple array ...
var objectItems = buildArray(myObj, "myObj");

// Now use them / test them etc... as you need to!
for (var x=0; x < objectItems.length; ++x) {
    console.log(objectItems[x].item + " = " + objectItems[x].value);
}

produces this in the console:

Javascript Code
myObj.pageURL = BLAH
myObj.emailBox.model = emailAddress
myObj.emailBox.selector = #emailAddress
myObj.passwordBox.model = password
myObj.passwordBox.selector = #password

Javascript Code
var myObj = {
    rrr: undefined,
    pageURL    : "BLAH",
    emailBox   : {model:"emailAddress", selector:"#emailAddress"},
    passwordBox: {model:"password"    , selector:"#password"},
    proba: {odin:{dva:"rr",trr:"tyuuu"}, od:{ff:5,ppa:{ooo:{lll:'lll'}},tyt:'12345'}}
};


function lookdeep(obj,p_Name,gg){
    var A=[], tem, wrem=[], dd=gg?wrem:A;
    for(var p in obj){
        var y1=gg?'':p_Name, y1=y1 + '.' + p;
        if(obj.hasOwnProperty(p)){
           var tem=obj[p];
           if(tem && typeof tem=='object'){
               a1=arguments.callee(tem,p_Name,true);
               if(a1 && typeof a1=='object'){for(i in a1){dd.push(y1 + a1[i])};}
Javascript Code
 }
            else{
               dd.push(y1 + ':' + String(tem));
            }
        }
    };
    return dd
};


var s=lookdeep(myObj,'myObj',false);
for (var x=0; x < s.length; ++x) {
console.log(s[x]+'\n');}

result:

Javascript Code
["myObj.rrr:undefined",
"myObj.pageURL:BLAH",
"myObj.emailBox.model:emailAddress",
"myObj.emailBox.selector:#emailAddress",
"myObj.passwordBox.model:password",
"myObj.passwordBox.selector:#password",
"myObj.proba.odin.dva:rr",
"myObj.proba.odin.trr:tyuuu",
"myObj.proba.od.ff:5",
"myObj.proba.od.ppa.ooo.lll:lll",
"myObj.proba.od.tyt:12345"]

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About the author

Venkatesan Prabu

Venkatesan Prabu

Wikitechy Founder, Author, International Speaker, and Job Consultant. My role as the CEO of Wikitechy, I help businesses build their next generation digital platforms and help with their product innovation and growth strategy. I'm a frequent speaker at tech conferences and events.

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