What are the methods for formatting numbers in JS?

The methods for formatting numbers in js include: toFixed() method converts the number to a number with a specified number of decimal places, toPrecision() method converts it to an exponential counting method when the specified number of decimal places is exceeded, and toExponential The () method converts the value to exponential notation

It is very useful to format numbers in JavaScript, but sometimes by forcing it to an integer, this method has a large error, so today I will share with you how to use it in JavaScript Several common methods for formatting numbers have a certain reference effect. I hope it will be helpful to everyone

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toFixed() method

can round the number to Number specifying the number of decimal places

Number.toFixed(num)

num: refers to the number of decimal places. Its value range is a value between 0 ~ 20, including 0 and 20. If this parameter is not written, 0 will be used to replace.

Return value

Returns the string representation of Number, which does not use the exponential counting method and has a fixed num digits after the decimal point. It can also be padded with 0s so that it reaches the length we specify. If the value we set is greater than length 21, this method will only call Number.toString() and return a string represented by exponential notation.

Note: When the value we set is too small or too large, an exception will be thrown, but the value between 0 ~ 20 will not cause this exception.

<script>
	var number=123.2344555
	console.log(number.toFixed(0));
	console.log(number.toFixed(4));
	console.log(number.toFixed(10));
</script>

The results are as follows:

toPrecision() method

means to convert the object to exponential notation when its value exceeds the specified number of digits.

Number.toPrecision(num)

num: refers to the minimum number of digits that must be converted to exponential notation. Its value range is between 1 ~ 21 (and includes 1 and 21). If this parameter is not written, the method toString() will be called instead of converting the number into a decimal value.

Return value

Returns a string of Number, including the valid digits set. If num is large enough to include all the digits in the integer part of Number, the returned string will be represented in fixed-point notation. Otherwise, exponential notation is used, with one digit before the decimal point and num-1 digits after the decimal point. The number is rounded or padded with zeros when necessary.

Note: When num is set too small or too large, an exception RangeError will be thrown

<script>
	var number=123.2344555
	console.log(number.toPrecision(1));
	console.log(number.toPrecision(4));
	console.log(number.toPrecision(10));
</script>

The results are as follows:

toExponential() method

can convert the value into exponential notation.

Number.toExponential(num)

num: refers to the number of decimal places in the exponential notation method, which is a value between 0 ~ 20 (including 0 and 20). If this parameter is not written, as many numbers as possible will be used.

Return value

The returned string is represented by exponential notation, that is, there is one digit before the decimal point and num digits after the decimal point. The decimal part of the number will be rounded, padded with zeros if necessary, to make it the specified length.

Note: When num is too small or too large, an exception RangeError will be thrown

<script>
	var number=123.2344555
	console.log(number.toExponential(1));
	console.log(number.toExponential(4));
	console.log(number.toExponential(10));
</script>

The results are as follows:

Summary: The above is That’s all in this article, I hope it will be helpful to everyone’s study.

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