@seval-ui/seval

> JavaScript-like language with native TypeScript runtime


@seval-ui/seval is a JavaScript-like language with a native TypeScript runtime for evaluating logic in UI applications.

Installation

``bash
npm install @seval-ui/seval


or


pnpm add @seval-ui/seval
`

Quick Start

`typescript
import { compileSeval, executeSeval } from '@seval-ui/seval'

// Compile Seval code to native JavaScript object
const code = {
double(x) { x * 2 },
add(a, b) { a + b }
}

const env = compileSeval(code)

// Call methods directly on the compiled object
const result1 = env.double(5)
console.log(result1) // 10

const result2 = env.add(3, 7)
console.log(result2) // 10

// Or use executeSeval for dynamic function calls
const result3 = executeSeval(env, 'double', [5])
console.log(result3) // 10

// With state management (this-based access)
const stateCode = {
count: 0,
increment() { this.count = this.count + 1 }
}
const stateEnv = compileSeval(stateCode)

// Execute with state tracking
const state = { count: 0 }
executeSeval(stateEnv, 'increment', [], state)
console.log(state.count) // 1
`

Features

- Compiles to native JavaScript – Uses new Function() for zero-overhead execution
- JavaScript-like syntax – Familiar syntax with arrow functions, objects, if/else, for loops
- Line comments – Use // for single-line comments
- Lightweight – No external dependencies for runtime evaluation
- Type-safe – Full TypeScript support with type definitions
- Sandbox protection – Blocks access to dangerous reflection properties

Syntax Overview

`javascript
{
// State properties
display: "0",
count: 0,

// Methods with implicit return (last expression)
increment() {
this.count = this.count + 1
},

// Single-expression functions
double(x) { x * 2 },

// Control flow with if/elif/else
action(value) {
if value > 0 {
this.display = "positive"
} elif value < 0 {
this.display = "negative"
} else {
this.display = "zero"
}
},

// For loops (three-part form)
sum() {
this.total = 0
for i = 0; i < 10; i = i + 1 {
this.total = this.total + i
}
this.total // Returns 45
},

// For loops (condition-only form)
countdown() {
for this.count > 0 {
this.count = this.count - 1
}
}
}
`

Built-in Primitives

The Seval runtime includes these built-in functions and globals:

- Arithmetic: +, -, *, /, % (+ also handles string concatenation)
- Comparison: ==, !=, ===, !==, <, <=, >, >=
- Logical: &&, ||, !
- Object helpers: merge(obj1, obj2, ...), get(obj, key)
- Globals: Math, Number, Date, String, Array, Object

Native JavaScript methods are accessible on values:
- String: s.length, s.substring(), s.includes(), s.startsWith(), s.concat()
- Array: arr.length, arr[index], arr.map(), arr.filter(), arr.concat(), arr.push()
- Object: obj.property, obj[key]`

License

MIT