3xpr 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
- 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
import { expressions as exp } from '3xpr'
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}}You can extend the library by adding enums, constants, formats, operators, and functions. To do this, use the following functions:
- AddConstant: Adds a constant to the library.
- AddEnum: Adds an enumeration to the library.
- AddFormat: Adds a format to the library.
- AddOperator: Adds an operator to the library.
- AddFunction: Adds a function to the library.
import { expressions as exp } from '3xpr'
const CryptoJS = require('crypto-js')
exp.addFunction(
'encrypt(value:string):string',
(value: string, key:string):string => CryptoJS.AES.encrypt(value, key).toString(),
{ description: 'Encrypt a string' }
)
exp.addFunction(
'decrypt(value:string):string',
(value: string, key:string):string => CryptoJS.AES.decrypt(value, key).toString(CryptoJS.enc.Utf8),
{ description: 'Decrypt a string' }
)Full documentation is available in the Wiki.