expressRangeValidator.js

A library of digital expression range validator.

This is a javascript library, it allow you to dynamic setting validation expression from your backend, so you don't need to change your front end codes while the value range is changed.

While filling a form with lots of fields which field type is digital, and you need to do some range validation for all the fields, such as the field value should be greater than 10, then the expression can be like this X>10 or 10<X. Normally, you may use eval() to figure out your express, but in some environment the eval function was disable, so you can just pass the expression X>10 and the value into this library's function and you get a result.

How to Use

The following codes shows how to refer a library and use it for you project.

Import the library

const ERValidator = require("./lib/index");

Validation result

runResult: false means don't pass validation; true means pass validation
runResultCode: 0 validation is success; 1 validation is fail; 2 wrong express

Normal express

let iExpress = 'x<10';
let validator = new ERValidator(iExpress, 9.0);
console.log(`${iExpress}`+' x= 9.0 : ', validator.runResult); // true
console.log('validator.runResultCode', validator.runResultCode); // 0

let iExpress = 'x<=10, x>20.1';
let validator = new ERValidator(iExpress, 15.5);
console.log(`${iExpress}`+' x= 15.5 : ', validator.runResult); // false
console.log('validator.runResultCode', validator.runResultCode); // 1

// variable 'Pa' is not equal to 'X', so need to set the options {toX: true}
let iExpress = 'Pa<10,Pa>=20.1';
let validator = new ERValidator(iExpress, 25.5, {toX: true});
console.log(`${iExpress}`+ ' Pa = 25.5 : ', validator.runResult); // true
console.log('validator.runResultCode', validator.runResultCode); // 0

let iExpress = '10<Pa<20.1';
let validator = new ERValidator(`${iExpress}`, 15.5, {toX: true});
console.log(`${iExpress}`+ ' Pa = 15.5 : ',  validator.runResult); // true
console.log('validator.runResultCode', validator.runResultCode); // 0

Special symbol
your input expression may contains some special symbols, for example ≥, ≤, ≠...

let iExpress = 'x≥10, x≤20.1';
let special = [['≥', '>='], ['≤', '<=']];
validator = new ERValidator(iExpress, 15.5, {special});
console.log(`${iExpress}` + ' x = 15.5 : ', validator.runResult); // true

Enum express

let iExpress = '[CN, USA, JP, UK]';
let validator = new ERValidator(iExpress, 'CN');
console.log(`${iExpress}` + ' CN : ', validator.runResult);

'or' relation sequence express
All the expressions(only support 'x=N') in sequence, such as 'x=10 or x=11 or x=12 or x=12.88 or x=-1.78 ...'

let iExpress = 'x=10,x=11,x=12,x=12.88,x=-1.78';
let validator = new ERValidator(iExpress, 12.0);
console.log(`${iExpress}` + ' 12.0 : ', validator.runResult);

'or' relation sequence mix express
each unit expression is a mix expression and all in sequence, as following
exp1: (x>10 and x<20) or (x>30 and x<40) ==> '(x>10,x<20),(x>30,x<40)'
exp2: (10<x and x<=20) or (30<x and x<40) ==> '(10<x<=20),(30<x<40)'
exp3: (10<x and x<=20) or (30>x) ==> '(10<x<=20),(30>x)'
exp4: (10<x and x<20) or (10<x and x<40) ==> '(10<x<=20),(10<x<40)' // this situlation is true

let iExpress = '(10<x<=20),(30>x)';
let validator = new ERValidator(iExpress, 15);
console.log(`${iExpress}` + ' 15 : ', validator.runResult);

Wrong express
There are several wrong expresses. Because we can't tell the relationship between left part and right part of an express. Such as 10<X, 20.1<X, the left part is 10<X and righ part is 20.1<X, the relationship can be && or || , so these are wrong expresses.

let eExpress1 = '10<X, 20.1<X';
let eExpress2 = '10>X, 20.1>X';
let eExpress3 = 'X>10, X>20.1';
let eExpress4 = 'X<20.1, X<10';  
let validator = new ERValidator(eExpress1, 15.5);
console.log('validator.runResult', validator.runResult); // false
console.log('validator.runResult', validator.runResultCode); // 2

Note

Unsupported situlations

// situlation 1
let constVal = 'X<Math.PI';
let validator = new ERValidator(constVal, 3.0);

// situlation 2
let funVal = 'X<max(8, 19)';
let validator = new ERValidator(funVal, 15.5);

Feedback

Email Jonah Shun or open an issue

Licence

MIT