Question

我有一个测验程序的javascript代码，但我无法弄清楚如何返回最后一个上下文行的计算结果只有1个小数。有什么建议吗？

EndQuiz=function(){
                  canvas.removeEventListener('click',ProcessClick,false);
                  context.drawImage(quizbg, 0,0,550,90,0,0,550,400);
                  context.font = "20pt Georgia,Arial";
                  context.fillText("Thanks for finishing. ",20,80);
          context.fillText("This is how good you were:",20,120);
                  context.font = "16pt Georgia,Calibri,Arial";
                  context.fillText("Correct answers: "+String(rightanswers)+" of "+String(rightanswers+wronganswers),20,180);

          context.fillText("Correct: "+String(rightanswers/(wronganswers+rightanswers)*100)+"%",20,240);1

Answer 1

直接来自W3schools：

将数字转换为字符串，只保留两位小数：

var num = 5.56789;
var n=num.toFixed(2);

n的结果将是：

5.57

其余部分留给读者练习： - ）

Answer 2

这是一个可以截断小数的函数函数：

truncateDecimal = function(decimal, numDecimals) {
    var decString = ""+decimal;
    var dotIndex = decString.indexOf(".");
    var numChars = dotIndex + 1 + numDecimals;
    return parseFloat(decString.substring(0, numChars));
}

现在truncateDecimal(3010101.234, 1);会返回3010101.2。

字符串计算的小数

2 个答案: