JavaScript > Number Methods

Precision format in JavaScript

How to format a number to a specified precision in JavaScript?


Precision

Precision means accurate, toPrecision() is a method in JavaScript, in mathematics precision method is appliceble for while converting. Converting the decimals to approximate and accurate values. 

In JavaScript, by using toPrecision() method we can format a number to a specified length.

Formatting a number into particular specified length.

<p>Click the below button to format into 3 digit specified length</p>
<input type="button" value="Format" onclick="Function()" />
<p id="myId"></p>

<script>
    function Function() {
        var a = 1.74562;
        var r = a.toPrecision(3);
        document.getElementById("myId").innerHTML = r;
    }
</script>

We need to format the length of the decimal number in variable a to 3 digit approximate decimal number, for that we are using toPrecision() method. Onclick of the button "Format" in the HTML code fires the Function() in the <script> block, at the same time toPrecision(3) method formats the length of the decimal and return the specified length number as output.

OUTPUT

Formatting into different lengths with the same number.

<p>Click the below button to format into 3 digit specified length</p>
<input type="button" value="Format" onclick="Function()" />
<p id="myId"></p>

<script>
    function Function() {
        var a = 1.74562;

        var r =a.toPrecision() + "</br>" + a.toPrecision(1) + "</br>" +
            a.toPrecision(2) + "</br>" + a.toPrecision(3) + "</br>" +
            a.toPrecision(4) + "</br>" + a.toPrecision(5) + "</br>" +
            a.toPrecision(6) + "</br>" + a.toPrecision(7) + "</br>" ;
        document.getElementById("myId").innerHTML = r;
    }
</script>

Format into different lengths of same number

Onclick of the button gives the different format lengths of the same decimal number as per the input value.

OUTPUT

Formatting the length of nano (Very small) values.

<p>Click the below button to format into 3 digit specified length</p>
<input type="button" value="Format" onclick="Function()" />
<p id="myId"></p>

<script>
    function Function() {
        var a = 0.0758642;

        var r =a.toPrecision() + "</br>" + a.toPrecision(1) + "</br>" +
            a.toPrecision(2) + "</br>" + a.toPrecision(3) + "</br>" +
            a.toPrecision(4) + "</br>" + a.toPrecision(5) + "</br>" +
            a.toPrecision(6) + "</br>" + a.toPrecision(7) + "</br>" ;
        document.getElementById("myId").innerHTML = r;
    }
</script>

Formating the length of nano values

We are formating the length of nano value (0.0758642), nano values are vey samll values which starts like 0.0014512... Onclick of the button returns the formatted length digits as per the input values.

OUTPUT

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