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Judgment method: 1. Use "var reg = / ^\ d + (? =\. {0Magne1}\ dexpressions $| $) /" to define the regular expression object reg;2, use the "reg.test (specify value)" statement 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, javascript1.8.5 version, Dell G3 computer.

Javascript determines whether the specified value is positive or not

In javascript, regular expressions can be used to determine whether a specified value is positive.

Implementation code:

Function validate (num) {if (num! = 0) {var reg = / ^\ d + (? =\. {0jue 1}\ daut $| $) /; if (reg.test (num)) {console.log (num+ "is positive");} else {console.log (num+ "not positive") }} else {console.log ("0 is neither positive nor negative");}} 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 pattern. Returns true if there is a matching value in the string, false otherwise.

Syntax:

RegExpObject.test (string)

Extended knowledge: expressions for checking numbers

Number: ^ [0-9] * $

N-digit number: ^\ d {n} $

At least n-digit number: ^\ d {n,} $

The number of mmurn digits: ^\ d {mrecom n} $

Zero and non-zero numbers: ^ (0 | [1-9] [0-9] *) $

A number with up to two decimal places at the beginning of a non-zero: ^ ([1-9] [0-9] *) + (. [0-9] {1J2})? $

Positive or negative numbers with 1-2 decimal places: ^ (\ -)?\ d + (\. D {1jin2})? $

Positive, negative, and decimal: ^ (\-|\ +)?\ d + (\.\ d +)? $

A positive real number with two decimal places: ^ [0-9] + (. [0-9] {2})? $

A positive real number with 1 to 3 decimal places: ^ [0-9] + (. [0-9] {1jue 3})? $

Non-zero positive integers: ^ [1-9]\ During $or ^ ([1-9] [0-9] *) {1 ~ (st) 3} $or ^\ +? [1-9] [0-9] * $

Non-zero negative integers: ^\-[1-9] [] 0-9 "* $or ^-[1-9]\ dflowers $

Non-negative integer: ^\ dBy $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]\ dfloat $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 numbers: ^-([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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