我如何在Javascript中四舍五入一个数字?

如何在JavaScript中四舍五入一个数字?

Math.round()不起作用，因为它舍入到最接近的小数。

我不确定是否有更好的方法，而不是在小数点处分开，保留第一位。一定有……

当前回答

使用Math.floor()是做到这一点的一种方法。

更多信息:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor

2009-09-16 23:08:05

其他回答

Math.round(3.14159 * 100) / 100  // 3.14

3.14159.toFixed(2);              // 3.14 returns a string
parseFloat(3.14159.toFixed(2));  // 3.14 returns a number

Math.round(3.14159)  // 3
Math.round(3.5)      // 4
Math.floor(3.8)      // 3
Math.ceil(3.2)       // 4

2022-03-20 00:20:35

Math.floor(1+7/8)

2009-09-16 23:14:02

使用Math.floor()是做到这一点的一种方法。

更多信息:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/floor

2009-09-16 23:08:05

你需要用-1来四舍五入，然后像下面的例子一样乘以-1。

<script type="text/javascript">

  function roundNumber(number, precision, isDown) {
    var factor = Math.pow(10, precision);
    var tempNumber = number * factor;
    var roundedTempNumber = 0;
    if (isDown) {
      tempNumber = -tempNumber;
      roundedTempNumber = Math.round(tempNumber) * -1;
    } else {
      roundedTempNumber = Math.round(tempNumber);
    }
    return roundedTempNumber / factor;
  }
</script>

<div class="col-sm-12">
  <p>Round number 1.25 down: <script>document.write(roundNumber(1.25, 1, true));</script>
  </p>
  <p>Round number 1.25 up: <script>document.write(roundNumber(1.25, 1, false));</script></p>
</div>

2017-10-25 13:00:39

这是数学。在一个简单的例子中使用地板。这可能会帮助新开发人员了解如何在函数中使用它以及它的功能。希望能有所帮助!

<script>

var marks = 0;

function getRandomNumbers(){    //  generate a random number between 1 & 10
    var number = Math.floor((Math.random() * 10) + 1);
    return number;
}

function getNew(){  
/*  
    This function can create a new problem by generating two random numbers. When the page is loading as the first time, this function is executed with the onload event and the onclick event of "new" button.
*/
document.getElementById("ans").focus();
var num1 = getRandomNumbers();
var num2 = getRandomNumbers();
document.getElementById("num1").value = num1;
document.getElementById("num2").value = num2;

document.getElementById("ans").value ="";
document.getElementById("resultBox").style.backgroundColor = "maroon"
document.getElementById("resultBox").innerHTML = "***"

}

function checkAns(){
/*
    After entering the answer, the entered answer will be compared with the correct answer. 
        If the answer is correct, the text of the result box should be "Correct" with a green background and 10 marks should be added to the total marks.
        If the answer is incorrect, the text of the result box should be "Incorrect" with a red background and 3 marks should be deducted from the total.
        The updated total marks should be always displayed at the total marks box.
*/

var num1 = eval(document.getElementById("num1").value);
var num2 = eval(document.getElementById("num2").value);
var answer = eval(document.getElementById("ans").value);

if(answer==(num1+num2)){
    marks = marks + 10;
    document.getElementById("resultBox").innerHTML = "Correct";
    document.getElementById("resultBox").style.backgroundColor = "green";
    document.getElementById("totalMarks").innerHTML= "Total marks : " + marks;

}

else{
    marks = marks - 3;
    document.getElementById("resultBox").innerHTML = "Wrong";
    document.getElementById("resultBox").style.backgroundColor = "red";
    document.getElementById("totalMarks").innerHTML = "Total Marks: " + marks ;
}




}

</script>
</head>

<body onLoad="getNew()">
    <div class="container">
        <h1>Let's add numbers</h1>
        <div class="sum">
            <input id="num1" type="text" readonly> + <input id="num2" type="text" readonly>
        </div>
        <h2>Enter the answer below and click 'Check'</h2>
        <div class="answer">
            <input id="ans" type="text" value="">
        </div>
        <input id="btnchk" onClick="checkAns()" type="button" value="Check" >
        <div id="resultBox">***</div>
        <input id="btnnew" onClick="getNew()" type="button" value="New">
        <div id="totalMarks">Total marks : 0</div>  
    </div>
</body>
</html>

2018-10-10 03:09:47

我如何在Javascript中四舍五入一个数字?

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