How to determine whether it is a decimal in ES6

Two judgment methods: 1. Use the test() function with the regular expression "/[.]/" to check whether the specified value contains a decimal point, the syntax is "/[.]/.test(specified value) ”, if included, it is a decimal, otherwise it is not. 2. Use the indexOf() function to check whether the specified value contains a decimal point. The syntax is "String(specified value).indexOf(".")". If the return value is greater than "-1", it is a decimal, and vice versa.

The operating environment of this tutorial: Windows 7 system, ECMAScript version 6, Dell G3 computer.

Decimals are "." with a decimal point. In JavaScript, you can determine whether a number is a decimal by judging whether it contains "." with a decimal point. .

Method 1: Use the test() function with regular expressions to check

The test() method is used to detect whether a string matches a certain pattern. , searches the string for text that matches the regular expression. If a match is found, it returns true; otherwise, it returns false.

RegExpObject.test(string)

Regular expression for checking decimals: /[.]/

Example:

function isDot(num) {
	var rep=/[.]/;
	if(rep.test(num)){
		console.log(num+" 是小数");
	}
	else{
		console.log(num+" 不是小数");
	}
}
isDot(121.121);//是小数
isDot(454.654);//是小数
isDot(454654);//不是小数

Method 2: Use the indexOf() function to check

The indexOf() method can return the position where a specified string value first appears in the string.

string.indexOf(searchvalue,start)

Parameters	Description
searchvalue	Required . Specifies the string value to be retrieved.
start	Optional integer parameter. Specifies the position in the string to begin searching. Its legal values ​​are 0 to string Object.length - 1. If this parameter is omitted, the search will start from the first character of the string.

Return value: Find the first occurrence of the specified string. If no matching string is found, -1 will be returned.

Just use indexOf() to check the position where the character "." first appears in the string. If the return value is equal to -1, it is a decimal, greater than -1 is not a decimal.

Example:

function isDot(num) {
	if(String(num).indexOf(".")>-1){
		console.log(num+" 是小数");
	}
	else{
		console.log(num+" 不是小数");
	}
}
isDot(121.121);//含有小数点
isDot(454654);//不含小数点
isDot(45465.4);//含小数点

[Recommended learning: javascript advanced tutorial]

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