9.5 JS 2017

JavaScript String Padding

ECMAScript 2017 added two String methods: padStart and padEnd to support padding at the beginning and at the end of a string.

Example 1: JS Strings - The padStart() Method

let str = "5";
str = str.padStart(4,0);
// result is 0005

Example 2: JS Strings - The padEnd() Method

let str = "5";
str = str.padEnd(4,0);
// result is 5000

• String Padding is not supported in Internet Explorer.
• Firefox and Safari were the first browsers with support for JavaScript string padding:

Chrome 57	Edge 15	Firefox 48	Safari 10	Opera 44
Mar 2017	Apr 2017	Aug 2016	Sep 2016	Mar 2017

JavaScript Object Entries

ECMAScript 2017 adds a new Object.entries method to objects:

Example 3: JS Object Methods - Object.entries() method

const person = {
  firstName : "John",
  lastName : "Doe",
  age : 50,
  eyeColor : "blue"
};
document.getElementById("demo").innerHTML = Object.entries(person);

Chrome and Firefox were the first browsers with support for Object.entries:

Chrome 47	Edge 14	Firefox 47	Safari 10.1	Opera 41
Jun 2016	Aug 2016	Jun 2016	Mar 2017	Oct 2016

JavaScript Object Values

Object.values are similar to Object.entries, but returns a single dimension array of the object values:

Example 4: JS Object Methods - Object.values() method

const person = {
  firstName : "John",
  lastName : "Doe",
  age : 50,
  eyeColor : "blue"
};
document.getElementById("demo").innerHTML = Object.values(person);

Firefox and Chrome were the first browsers with support for Object.values:

Chrome 54	Edge 14	Firefox 47	Safari 10.1	Opera 41
Oct 2016	Aug 2016	Jun 2016	Mar 2017	Oct 2016

JavaScript Async Functions

Waiting for a Timeout

async function myDisplay() {
  let myPromise = new Promise(function(myResolve, myReject) {
    setTimeout(function() { myResolve("I love You !!"); }, 3000);
  });
  document.getElementById("demo").innerHTML = await myPromise;
}

myDisplay();

Firefox and Chrome were the first browsers with support for async JavaScript functions:

Chrome 55	Edge 15	Firefox 52	Safari 11	Opera 42
Dec 2016	Apr 2017	Mar 2017	Sep 2017	Dec 2016