javascript - Why is my for loop stopping after one iteration? - Stack Overflow

admin管理员组

文章数量:1344533

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

Share Improve this question Follow edited Aug 27, 2009 at 20:16 chaos 124k3434 gold badges306306 silver badges310310 bronze badges asked Aug 27, 2009 at 13:12 wheresrhyswheresrhys 23.6k2121 gold badges9696 silver badges165165 bronze badges 2

• 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

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 11

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.

本文标签： javascriptWhy is my for loop stopping after one iterationStack Overflow