Getting the values for a specific key from all objects in an array

You could map:

permittedValues = array.map(function(value) {
  return value.key;
});

In ES6/ES2015 it's even prettier with arrow functions:

permittedValues = array.map(value => value.key);

It might be prettier, but it's probably not faster than a for() loop.

Using lodash,

Since lodash 4.x the _.pluck function has been removed in support to map function.

so you can achieve the desired task by:

import _ from 'lodash'
_.map(items, 'key');

Ref: What happened to Lodash _.pluck?

Pure Javascript ES6

array.map(value => value.key);

Underscore/Lodash

_.map(value,'key')

If you are using ES6 javascript version you can do something like the one below:

const arrayData = [
    {
        key: 'blah',
        value: 'Blah Blah'
    },
    {
        key: 'foo',
        value: 'Foos'
    },
    {
        key: 'bar',
        value: 'Bars'
    },
    {
        key: 'baz',
        value: 'Bazingo'
    }
];
const foodBar = arrayData.find(item => item.key === "baz");
const resultValue = foodBar['value']; // here the extracted value is by key