Racking my brains on this one. I have the code below: the first stages of a JavaScript game. All the objects are well-defined and I'm using jQuery for DOM interaction. The puzzle is created with the following JS code:

var mypuzzle = new puzzle("{solution:'5+6+89',equations:[['5+3=8',23,23],['5+1=6',150,23],['5+3=6',230,23]]}");

However, the loop at the bottom of the code won't go further than the first iteration. Any idea why? No errors are thrown at all.

function equationBox(equation, top, left) {//draggable equation box
    this.reposition = function() {
        this.top = 0;
        this.left = 0;
    }
    this.top = 0;//make random
    this.left = 0;//make random
    this.equation = equation;
    if(top && left) {
        this.top = top; 
        this.left = left;
    }
    this.content = this.equation.LHS.string + '<span> = </span>' + this.equation.RHS.string;
    this.DOM = $('<li>').html(this.content);
}


function puzzle(json) {

    this.addEquationBox = function(equationBox) {
        $('#puzzle #equations').append(equationBox.DOM);
    }

    this.init = function() {
        //this.drawPuzzleBox();
        this.json = JSON.parse(json);
        this.solution = new expression(this.json.solution || '');
        this.equations = this.json.equations || [];
        var iterations = this.equations.length;
        for(i=0;i<iterations;i++)
        {
            console.log(i);
            this.addEquationBox(new equationBox(stringToEquation(this.equations[i][0]),this.equations[i][1], this.equations[i][2])); 
        }
    }
    this.init();
}

Racking my brains on this one. I have the code below: the first stages of a JavaScript game. All the objects are well-defined and I'm using jQuery for DOM interaction. The puzzle is created with the following JS code:

var mypuzzle = new puzzle("{solution:'5+6+89',equations:[['5+3=8',23,23],['5+1=6',150,23],['5+3=6',230,23]]}");

However, the loop at the bottom of the code won't go further than the first iteration. Any idea why? No errors are thrown at all.

function equationBox(equation, top, left) {//draggable equation box
    this.reposition = function() {
        this.top = 0;
        this.left = 0;
    }
    this.top = 0;//make random
    this.left = 0;//make random
    this.equation = equation;
    if(top && left) {
        this.top = top; 
        this.left = left;
    }
    this.content = this.equation.LHS.string + '<span> = </span>' + this.equation.RHS.string;
    this.DOM = $('<li>').html(this.content);
}


function puzzle(json) {

    this.addEquationBox = function(equationBox) {
        $('#puzzle #equations').append(equationBox.DOM);
    }

    this.init = function() {
        //this.drawPuzzleBox();
        this.json = JSON.parse(json);
        this.solution = new expression(this.json.solution || '');
        this.equations = this.json.equations || [];
        var iterations = this.equations.length;
        for(i=0;i<iterations;i++)
        {
            console.log(i);
            this.addEquationBox(new equationBox(stringToEquation(this.equations[i][0]),this.equations[i][1], this.equations[i][2])); 
        }
    }
    this.init();
}

• javascript
• oop
• scope
• loops
• for-loop

• Where is JSON.parse defined? – Daniel Vandersluis Commented Aug 27, 2009 at 13:32
• What happens when you debug this? – Charlie Commented Aug 27, 2009 at 13:32

3 Answers 3

Possibly your failure to scope your counter variable is doing it, especially if you make a habit of it (since you're using the global variable of that name, and any loops you wrote in any code you're calling may be doing the same thing). Try:

for(var i=0;i<iterations;i++)

because this.equations = this.json.equations || [] , and, since this.json.equations is undefined, it get assigned to []

Assuming you're using JSON.parse as defined at https://github./douglascrockford/JSON-js/blob/master/json2.js, it appears that your json string is not parsing properly:

var string1 = "{solution:'5+6+89',equations:[['5+3=8',23,23],['5+1=6',150,23],['5+3=6',230,23]]}"
JSON.parse(string1); // throws SyntaxError("JSON.parse")

When I use JSON.stringify, defined in the same file, to create a JSON string from your object:

var obj = {solution:'5+6+89',equations:[['5+3=8',23,23],['5+1=6',150,23],['5+3=6',230,23]]}
var string2 = JSON.stringify(obj);
// {"solution":"5+6+89","equations":[["5+3=8",23,23],["5+1=6",150,23],["5+3=6",230,23]]}
JSON.parse(string2); // returns a proper object

Note that the string that JSON.stringify is creating is different than the one you are trying to use, which might be the cause of your problem.