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How to use toPrecision function

不言Original: 2019-02-19 17:36:582227browse

The toPrecision() function in Javascript is used to format numbers to a specific precision or length. If the formatted number requires more digits than the original number, decimals and null values are also added to create the specified length. Let's take a look at the specific use of the toPrecision function.

Let’s first take a look at the basic syntax of the toPrecision function

number .toPrecision（value）

toPrecision function accepts a single parameter value, this parameter is optional , which represents the number of significant digits the user needs in a formatted number.

Let’s look at a specific example

No parameters are passed in the toPrecision() method:If no parameters are passed to the toPrecision() function, the formatted number will be exactly the same as entering a number. However, it will be represented as a string rather than a number.

The code is as follows

<!DOCTYPE html>
<html>
<head>
  <title></title>
</head>
<body>
<script type="text/javascript"> 
    var num=213.45689; 
    document.write(num.toPrecision());           
</script> 
</body>
</html>

The output result is: 213.45689

Pass parameters in the toPrecision() function: If the precision passed to the toPrecision() function If the length is less than the original number, the number will be rounded to that precision.

The code is as follows

<!DOCTYPE html>
<html>
<head>
  <title></title>
</head>
<body>
<script type="text/javascript"> 
    var num=213.45689; 
    document.write(num.toPrecision(4));           
</script> 
</body>
</html>

The output result is: 213.5

Pass a parameter, which will cause a null value to appear in the output: If passed to toPrecision () function has a precision length greater than the original number, appends a zero value to the input number to satisfy the specified precision.

The code is as follows

<!DOCTYPE html>
<html>
<head>
  <title></title>
</head>
<body>
<script type="text/javascript"> 
    var num=213.45689; 
    document.write(num.toPrecision(12)+"<br>");   
    var num2 = 123; 
    document.write(num2.toPrecision(5));         
</script> 
</body>
</html>

The output result is as follows

213.456890000
123.00

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