How to List the Properties of a JavaScript Object

How to list the properties of a JavaScript object?

In modern browsers (IE9+, FF4+, Chrome5+, Opera12+, Safari5+) you can use the built in Object.keys method:

var keys = Object.keys(myObject);

The above has a full polyfill but a simplified version is:

var getKeys = function(obj){
   var keys = [];
   for(var key in obj){
      keys.push(key);
   }
   return keys;
}

Alternatively replace var getKeys with Object.prototype.keys to allow you to call .keys() on any object. Extending the prototype has some side effects and I wouldn't recommend doing it.

How to get all properties values of a JavaScript Object (without knowing the keys)?

By using a simple for..in loop:

for(var key in objects) {
    var value = objects[key];
}

How to get the list of object properties in javascript?

You can use Object.keys() to get array of keys in an object.

How to list the properties of a JavaScript object by field name

You can use .map

var data = data.map(function (el) {
   return el.Email
})

How to get a subset of a javascript object's properties

Using Object Destructuring and Property Shorthand

const object = { a: 5, b: 6, c: 7  };

const picked = (({ a, c }) => ({ a, c }))(object);

console.log(picked); // { a: 5, c: 7 }