expressions-parser

expressions-parser allows you to parse expression from string and evaluate it.

Install:

npm i expressions-parser

How to use:

import {toAST, parseInput, apply} from 'expressions-parser';

const ast = toAST(parseInput('1 + 1'));
apply(ast, {}); // return 2

Expressions syntax

Allowed are:

• numbers: 1, 100500, -1
• strings (both single and double quoted): 'test string', "another string"
• boolean: false, true
• object field access: obj.field
• indexed access: field[0], field['property'], field[propVariable]
• method call: obj.method(), obj.method(arg1, 'arg2', 0)

Pipes

You can use pipes the same way as in angular:

import {toAST, parseInput, apply} from 'expressions-parser';
const ast = toAST(parseInput('obj.numbers | min:10 | sum'));
const sum = apply(ast, {
    obj: {
        numbers: [1, 2, 11, 19, 15]
    }
}, {
    pipes: {
        min: (arr: number[], min: number) => arr.filter(x => x >= min),
        sum: (arr: number[]) => arr.reduce((a, b) => a + b, 0)
    }
}); // returns 45