Expression-language.js

Expression-language.js is an engine for javascript that can compile and evaluate expressions written in typescript.

Installation

Install via npm.

npm install expression-language.js --save

or yarn.

yarn add expression-language.js

Getting Started

Example:

import {Evaluator} from "expression-language.js";

const evaluator = new Evaluator();

// assume your have the following expr.
const expr = "user.ip in allowedIps and user.role is 'admin'";

const context = {
    user: {
        ip: "127.0.0.1",
        role: "admin"
    },
    allowedIps: ["127.0.0.1", "... other ip"]
};

if (evaluator.evaluate(expr, context)) {
    // yes. you're allowed.
    doSomething();
}

Supported binary & unary.

Binary

| Operator | Sample |
| --- | --- | | or | alias of || | | || | a || b | | and | alias of && | | && | a && b | | | | a | b | | ^ | a ^ b | | & | a & b | | == | a == b | | === | a === b | | is | alias of === | | != | a != b | | !== | a !== b | | < | a < b | | > | a > b | | >= | a >= b | | <= | a <= b | | in | 10 in [8,10,12] | | << | a << b | | >> | a >> b | | + | a + b | | - | a - b | | ~ | a ~ b | | * | a * b | | / | a / b | | % | a % b |

Unary

| Operator | Sample| | --- | --- | | + | +10 | | - | -10 | | ! | !a | | not | alias of ! | | ++ | ++ a or a ++| | -- | -- a or a --|

Function call.

evaluator.evaluate('say("hello", "world")', {
    say: function (left, right) {
        return left + ' ' + right;
    }
});

// will output "hello world".

Method also supported.

evaluator.evaluate('people.say("hello", "world")', {
    people: {
        say: function (left, right) {
            return left + ' ' + right;
        }
    }
});

You can write multi expressions, separated by SEMICOLON(;); However, evaluator will only return the value of the last expr.

evaluator.evaluate('12; "abc"'); //will ouput "abc"

Assign statement is also supported.

evaluator.evaluate('a = 10; a + 2'); //will ouput 12

LICENSE

The MIT license. See MIT