JavaScript Array map() Method

In the example below, height returns an array of height values.  The map function takes a function with one argument (in this case, image), which is a reference to an array element.  The return value of this function will be used as an item in the resulting array.

var images = [
  { height: '34px', width: '39px' },
  { height: '54px', width: '19px' },
  { height: '83px', width: '75px' },
];

var heights = images.map(function(image){
    return image.height;
});

console.log(heights);

Here’s the same function using the arrow notation, which is more concise:

var images = [
  { height: '34px', width: '39px' },
  { height: '54px', width: '19px' },
  { height: '83px', width: '75px' },
];

var heights = images.map((image)=>{return image.height});

console.log(heights);

In the following example, the pluck function generates an array of property values.  The first argument is an array of objects and the second argument is the property name.

var trips = [
  { distance: 34, time: 10 },
  { distance: 90, time: 50 },
  { distance: 59, time: 25 }
];

function pluck(array, property) {
    return array.map(function(item){
        return item[property];   
    });
}
console.log(pluck(trips,'distance'));