Js-expressions NPM

js-expressions

Js-expression is an extensible expression evaluator and parser.
Besides the operators, functions, variables, objects and arrays that are supported.
It is possible to extend it with your own functions, operators, etc

Features

Constants, enums, number, string, datetime, variables, objects and array
Arithmetic , assignment , comparison , logical and bitwise operators
Number , string , datetime , array and nullable functions
Conversion functions
Arrow functions
Group functions (distinct, first, last, min, max, sum and avg)
Sets functions (union, intersection, difference and symmetric difference)
Control flows flows
Environment variables
Extend
Metadata

Quick start

import { expressions as exp } from 'js-expressions'

const context = {
name: 'Spain',
region: 'Europe',
phoneCode: '34',
timezones: [
	{ name: 'Madrid', offset: 1, pos: { lat: 40.4165, log: -3.70256 } },
	{ name: 'Ceuta', offset: 1, pos: { lat: 35.8883, log: -5.3162 } },
	{ name: 'Canary', offset: 0, pos: { lat: 28.1248, log: -15.43 } }
	]
}

const result = exp.eval('5*(7+9)==(5*7+5*9)')
console.log(result)
// Output: true

// use context
exp.eval('toNumber(phoneCode) <= 30', context)
// false

// template
exp.eval('`${name} belongs to ${region}`', context)
// 'Spain belongs to Europe'

exp.eval('timezones.filter(p => substring(p.name,0,1)=="C")', context)
// ['{"name":"Ceuta","offset":1,"pos":{"lat":35.8883,"log":-5.3162}}'
// ,'{"name":"Canary","offset":0,"pos":{"lat":28.1248,"log":-15.43}}']

exp.eval('timezones.filter(p => p.offset == 1).sort(p => p.pos.lat).name', context)
// ['Ceuta','Madrid']

exp.eval('stringify(timezones.first(p => p.name == "Madrid").pos)', context)
// '{"lat":40.4165,"log":-3.70256}'

exp.eval('timezones.filter(p => p.pos.lat > 30 && p.pos.log > -4).pos.lat', context)
// [40.4165]

exp.eval('sort(timezones.name)', context)
// ['Canary','Ceuta','Madrid']

exp.eval('timezones[0].name', context)
// 'Madrid'

exp.eval('round(timezones.first(p=> p.name =="Madrid").pos.lat - timezones.first(p=> p.name =="Ceuta").pos.lat,2)', context)
// 4.55

exp.eval('timezones.each(p => p.pos={lat:round(p.pos.lat,2),log:round(p.pos.log,2)}).map(p=> stringify(p))', context)
// ['{"name":"Madrid","offset":1,"pos":{"lat":40.4,"log":-3.7}}'
// ,'{"name":"Ceuta","offset":1,"pos":{"lat":35.9,"log":-5.3}}'
// ,'{"name":"Canary","offset":0,"pos":{"lat":28.1,"log":-15.45}}']

exp.eval(`
list = [1, 2, 3, 4, 5, 6, 7, 8, 9];
total = 0;
for (i = 0; i < list.length(); i += 1) {
	total += list[i];
}
`, context)
console.log(context.total)
// 45

exp.eval(`
while (p=timezones.pop()) {
	console(p);
}
`, context)
// outputs:
//         {"name":"Canary","offset":0,"pos":{"lat":28.1,"log":-15.45}}
//         {"name":"Ceuta","offset":1,"pos":{"lat":35.9,"log":-5.3}}
//         {"name":"Madrid","offset":1,"pos":{"lat":40.4,"log":-3.7}}