How to determine whether a specified value is a positive number in javascript

Judgment method: 1. Use the "var reg = /^\d (?=\.{0,1}\d $|$)/" statement to define the regular expression object reg; 2. Use " The reg.test(specified value)" statement uses regular expressions to determine whether the specified value is a positive number. If it returns true, it is a positive number, otherwise it is not a positive number.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

javascript determines whether the specified value is a positive number

In javascript, you can use regular expressions to determine whether the specified value is a positive number.

Implementation code:

function validate(num) {
	if (num != 0) {
		var reg = /^\d+(?=\.{0,1}\d+$|$)/;
		if (reg.test(num)) {
			console.log(num+" 是正数");
		} else {
			console.log(num+" 不是正数");
		}
	}
	else{
		console.log("0既不是正数也不是负数");
	}
}
validate(-1);
validate(-2);
validate(0);
validate(1);
validate(1.5);
validate(2.365);

Description: The

test() method is used to detect whether a string matches a certain pattern. Returns true if there is a matching value in the string, false otherwise.

Grammar:

RegExpObject.test(string)

Extended knowledge: expressions to check numbers

• Numbers: ^[0-9]*$

• n-digit number: ^\d{n}$
  

• At least n-digit number: ^\d{n,}$

• ##m-n-digit number:

  ^\d{ m,n}$

• Numbers starting with zero and non-zero:

  ^(0|[1-9][0-9]*)$

• Numbers starting with non-zero and with up to two decimal places:

  ^([1-9][0-9]*) (.[0-9]{ 1,2})?$

• Positive or negative number with 1-2 decimal places:

  ^(\-)?\d (\.\d {1,2})?$

• Positive numbers, negative numbers, and decimals:

  ^(\-|\ )?\d (\.\d ) ?$

• Positive real number with two decimal places:

  ^[0-9] (.[0-9]{2})?$

• Positive real numbers with 1 to 3 decimal places:

  ^[0-9] (.[0-9]{1,3})?$

• Non-zero positive integer:

  ^[1-9]\d*$ or ^([1-9][0-9]* ){1,3}$ or ^\ ?[1-9][0-9]*$

• Non-zero negative integer:

  ^\-[1-9][]0-9"*$ or ^-[1-9]\d*$

• Non-negative integer:

  ^\d $ or ^[1-9]\d*|0$

• Non-positive integer ：

  ^-[1-9]\d*|0$ or ^((-\d )|(0 ))$

• Non-negative floating point number:

  ^\d (\.\d )?$ or ^[1-9]\d*\.\d*|0\.\d*[ 1-9]\d*|0?\.0 |0$

• Non-positive floating point number:

  ^((-\d (\.\d )?)|(0 (\.0 )?))$ or ^(-([1-9]\d*\.\d*|0\.\d*[1-9 ]\d*))|0?\.0 |0$

• Positive floating point number:

  ^[1-9]\d*\.\d *|0\.\d*[1-9]\d*$ or ^(([0-9] \.[0-9]*[1-9][0-9] *)|([0-9]*[1-9][0-9]*\.[0-9] )|([0-9]*[1-9][0-9]*)) $

• Negative floating point number:

  ^-([1-9]\d*\.\d*|0\.\d*[1-9 ]\d*)$ or ^(-(([0-9] \.[0-9]*[1-9][0-9]*)|([0-9] *[1-9][0-9]*\.[0-9] )|([0-9]*[1-9][0-9]*)))$

• Floating point number:

  ^(-?\d )(\.\d )?$ or ^-?([1-9]\d*\. \d*|0\.\d*[1-9]\d*|0?\.0 |0)$

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