为什么我的for循环在一次迭代后停止?

在这件事上绞尽脑汁。我有下面的代码:JavaScript游戏的第一阶段。所有对象都定义良好,我使用jquery进行DOM交互。拼图是用以下JS代码创建的:

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

但是,代码底部的循环不会比第一次迭代更深入。你知道为什么吗?根本不会引发任何错误。

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();
}