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JavaScript ECMAScript 2019

Original JavaScript version numbers were ES5 (2009) and ES6 (2015)

New Features in ECMAScript 2019

This chapter introduces the new features in ECMAScript 2019:

  • String.trimStart()
  • String.trimEnd()
  • Array.flat()
  • Object.fromEntries
  • Optional catch binding

    • JavaScript String trimStart()

    ECMAScript 2019 added the String method trimStart() to JavaScript.

    The trimStart() method works like trim(), but removes whitespace only from the start of a string.

    Example

    let text1 = "     Hello World!     ";
    let text2 = text1.trimStart();

    JavaScript String trimStart() is supported in all browsers since January 2020:

    Chrome 66 Edge 79 Firefox 61 Safari 12 Opera 50
    Apr 2018 Jan 2020 Jun 2018 Sep 2018 May 2018

    JavaScript String trimEnd()

    ECMAScript 2019 added the String method trimEnd() to JavaScript.

    The trimEnd() method works like trim(), but removes whitespace only from the end of a string.

    Example

    let text1 = "     Hello World!     ";
    let text2 = text1.trimEnd();

    JavaScript String trimEnd() is supported in all browsers since January 2020:

    Chrome 66 Edge 79 Firefox 61 Safari 12 Opera 50
    Apr 2018 Jan 2020 Jun 2018 Sep 2018 May 2018

    JavaScript Array flat()

    ECMAScript 2019 added the Array method flat() to JavaScript.

    The flat() method nested Arrays into flat Arrays.

    Example

    const myArr = [[1,2],[3,4],[5,6]];
    const newArr = myArr.flat();

    JavaScript Array flat() is supported in all browsers since January 2020:

    Chrome 69 Edge 79 Firefox 62 Safari 12 Opera 56
    Sep 2018 Jan 2020 Sep 2018 Sep 2018 Sep 2018

    JavaScript Object fromEntries()

    ECMAScript 2019 added the Object method fromEntries() to JavaScript.

    The fromEntries() method creates an object from iterable key / value pairs.

    Example

    const fruits = [
    ["apples", 300],
    ["pears", 900],
    ["bananas", 500]
    ];

    const myObj = Object.fromEntries(fruits);

    JavaScript Object fromEntries() is supported in all browsers since January 2020:

    Chrome 73 Edge 79 Firefox 63 Safari 12.1 Opera 60
    Mar 2019 Jan 2020 Oct 2018 Mar 2019 Apr 2019

    Optional catch Binding

    From ECMAScript 2019 you can omit the catch parameter if you don't need it:.

    Example

    Before 2019:

    try {
    // code
    } catch (err) {
    // code
    }

    After 2019:

    try {
    // code
    } catch {
    // code
    }

    Optional catch binding is supported in all browsers since January 2020:

    Chrome 66 Edge 79 Firefox 58 Safari 11.1 Opera 53
    Apr 2018 Jan 2020 Jan 2018 Mar 2018 May 2018

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