JSLint Strict Violation. Object Oriented Javascript frustrations

javascript, jslint, strict, use-strict

Solution

You need to use your `piece` function as a constructor—in other words call it with the `new` keyword.

As it stands now, `this` inside of your function is the global object. Basically, instead of creating a new object, and adding properties to it, you're clobbering the gobal object with junk.

Since you're in strict mode, `this` will be undefined, so your code will error out.

This is what you want:

function Piece(color, type, x, y, captured, hasMoved) {
    "use strict";
    this.color = color;
    this.type = type;
    //...

var whitePawn1  = new Piece("white", "pawn", 0, 1, false, false);
var blackBishop1  = new Piece("black", "bishop", 8, 3, false, false);

Note that I renamed `piece` to start with a capital letter, since contructor functions by convention are supposed to.

Also, assuming a constructor function like this is really what you want, compared to Ian's answer, you should consider moving the `movePiece` function out to the function's prototype, so that function doesn't have to be re-created each and every time you create a new piece. So this

this.movePiece = movePiece;
function movePiece(x, y) {
   //...
}

would become this

//this goes **outside** of your function
Piece.prototype.movePiece = function movePiece(x, y) {
       //...
}

Problem

Original source