Ast-eval NPM | npm.io

ast-eval

Statically evaluate expressions in AST, also known as constants folding. Useful for precompilation tasks.

Use

npm install --save ast-eval

var esprima = require('esprima');
var gen = require('escodegen').generate;
var astEval = require('ast-eval');

var ast = esprima.parse('[1, 2 === "2", 3+4*10, [2] === 2]');
ast = astEval(ast);

gen(ast); //'[1, false, 43, false]'

API

preeval(Node, options) → Node

Evaluate expressions in a Node, return a new Node with optimized shorten expression nodes.

Features

Fold expressions x Binary expressions: `1000 60 60→36e6` x Logical expressions: {a:1} && {b:2} → true * x Math expressions: Math.sin(Math.Pi / 2 ) → 1
Fold arrays x Safe methods: [1,2,3,new Date].concat(4, [5], new Date) → [1,2,3,new Date,4,5, new Date] x Unsafe methods: [1,2,3].map(function(x){ return x*2}) → [2,4,6] Static methods: `Array.from(1, 2, 3, function(x){ return x2; })→2,4,6* [ ] Prototype methods:Array.prototype.slice.call(1,2,3, 1,2)→2`
Fold static globals (what’s that?)
Decompute object access (optionally) * x a['x'] = 1 → a.x = 1
Fold strings * x 'a b c'.split(' ') → ['a', 'b', 'c']
Propagate constants Simple flow analysis: var x = 1; x + 2; → 3; Scope analysis * Method substitution: var slice = Array.prototype.slice; var x = [1,2,3]; var y = slice(x)'
Fold loops `var x = []; for (var i = 0; i < 10; i++) {xi = 10i;}`
Fold proxy functions
Remove unused props
Undead code Empty isolated functions Remove unused variables (after enabling constants) Remove unused functions Remove unused properties
Fold clone-code * a.x×3 → var _a = a; _a.x
Data-flow analysis Precall functions Substitute variables
Provide exports
Fold primitives new Array(1,2,3,...)
Rearrange things Hoist functions (place after first use) Fold variable declarations