Why am I getting a Syntax error when using "class" in Javascript

Question

I am making a game in javascript, and I'm using making a class to hold all the sprites. However when I try to run it, safari gives me "SyntaxError: Unexpected use of reserved word 'class'". I can't find a reason it should be doing this. Below is my code:

var spritesContext;

//Sprite class
class sprite{
    constructor(imageName, imageX, imageY, imageHeight, imageWidth, context, canvas){
        this.imageName = imageName;
        this.imageX = imageX;
        this.imageY = imageY;
        this.imageHeight = imageHeight;
        this.imageWidth = imageWidth;
        this.canvas = canvas;
        this.context = context;
        spritesContext = context;
        console.log("Sprite constructed");
    }

    draw(){
        var character = new Image();
        character.src = "../Images/" + this.imageName + ".png";
        character.onload = function(){
            spritesContext.drawImage(character, this.imageX, this.imageY, this.imageWidth, this.imageHeight);
            console.log("Inner Draw is working.");
        }
        console.log("Draw is working.");
    }

    function getHeight(){
        return this.imageHeight;
    }

    function getWidth(){
         return this.imageWidth;
    }

    function getX(){
        return this.imageX;
    }

    function getY(){
       return this.imageY;
    }

    function moveUpX(e){
        this.imageX = (this.imageX + e);
    }

    function moveUpY(e){
        this.imageY = (this.imageY + e);
    }

    function moveBackX(e){
        this.imageX = (this.imageX - e);
    }

    function moveBackY(e){
       this.imageY = (this.imageY - e);
    }

    function changeImage(e){
        this.imageName = e;
    }

    function getImage(){
       return this.imageName;
    }

    function changeX(e){
         this.imageX = e;
    }

    function changeY(e){
        this.imageY = e;
    }

}

"class" is a new thing -- what version of javascript engine are you using? — Soren
– Soren, Commented Mar 1, 2016 at 2:33
It's a keyword in ES6. What browser/environment are you using this in? — zero298
– zero298, Commented Mar 1, 2016 at 2:35
You can't declare functions inside a class like that, that's an error — adeneo
– adeneo, Commented Mar 1, 2016 at 2:46

Sarhanis · Accepted Answer · 2016-03-01 02:39:15Z

0

To make your code work, and more specifically the keyword class, you need to be in strict mode to enable certain browsers to interpret it.

To be in strict mode, add the following to the top of your file:

'use strict';

edited Mar 1, 2016 at 2:39

answered Mar 1, 2016 at 2:35

Sarhanis

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3 Comments

user1114 Over a year ago

To clarify a little: the language itself does not require strict mode to use these features, but the browsers that are rolling them out have enabled some in strict mode before standard mode.

Sarhanis Over a year ago

Updated my answer based on your comment. Thanks.

adeneo Over a year ago

And, at least Chrome is sensible enough to throw errors like ..class not yet supported outside strict mode, not Unexpected use...

shrimp rice · Accepted Answer · 2019-12-16 16:08:24Z

0

Safari did not support "class" when the question was asked.

answered Dec 16, 2019 at 16:08

shrimp rice

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