Rename the property names and change the values of multiple objects

Solution 1:

This seems to do the trick:

function changeData(data){
    var title;
    for(var i = 0; i < data.length; i++){
        if(data[i].hasOwnProperty("thumb")){
            data[i]["thumbnail"] = data[i]["thumb"];
            delete data[i]["thumb"];
        }

        if(data[i].hasOwnProperty("title")){ //added missing closing parenthesis
            title = data[i].title;
            data[i].title = '<span class="red">' + title + '</span>';
        }
    }
}

changeData(data);

EDIT:

I tried to make the function generic, but since you updated your answer to do very specific things, I've added the business logic to the function.

Solution 2:

You can iterate over the array, set a new property in each object, and delete the old property:

data.forEach(function(e) {
   e.thumbnail = e.thumb;
   delete e.thumb;    
});

Here's a working example (check the output in the console).

Obviously you'll want to use a polyfill for Array.prototype.forEach if you want to support older browsers (there's one in the MDN article I linked to above, or you could just use a normal for loop).

Solution 3:

I have created a nice function to rename properties names: https://github.com/meni181818/simpleCloneJS/blob/master/renameProperties.js

example:

var sourceObj = {
    foo: 'this is foo',
    bar: {baz: 'this is baz',
          qux: 'this is qux'}
};
//                                the source, rename list
var replacedObj = renameProperties(sourceObj, {foo: 'foooo', qux: 'quxxxx'});
// replacedObj output => {
        foooo: 'this is foo',
        bar: {baz: 'this is baz',
              quxxxx: 'this is qux'}
    };

Since you are using Jquery you can use $.each function inside this function:

function renameProperties(sourceObj, replaceList, destObj) {
    destObj = destObj || {};
    $.each(sourceObj, function(key) {
        if(sourceObj.hasOwnProperty(key)) {
            if(sourceObj[key] instanceof Array) {
                if(replaceList[key]) {
                    var newName = replaceList[key];
                    destObj[newName] = [];
                    renameProperties(sourceObj[key], replaceList, destObj[newName]);
                } else if(!replaceList[key]) {
                    destObj[key] = [];
                    renameProperties(sourceObj[key], replaceList, destObj[key]);
                }
            } else if(typeof sourceObj[key] === 'object') {
                if(replaceList[key]) {
                    var newName = replaceList[key];
                    destObj[newName] = {};
                    renameProperties(sourceObj[key], replaceList, destObj[newName]);
                } else if(!replaceList[key]) {
                    destObj[key] = {};
                    renameProperties(sourceObj[key], replaceList, destObj[key]);
                }
            } else {
                if(replaceList[key]) {
                    var newName = replaceList[key];
                    destObj[newName] = sourceObj[key];
                } else if(!replaceList[key]) {
                    destObj[key] = sourceObj[key];
                }
            }
        }
    });
    return destObj;
}

demo: http://jsfiddle.net/g2jzse5k/