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88 lines
2.0 KiB
88 lines
2.0 KiB
5 years ago
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# static-eval
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evaluate statically-analyzable expressions
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[](https://ci.testling.com/substack/static-eval)
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[](http://travis-ci.org/substack/static-eval)
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# security
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static-eval is like `eval`. It is intended for use in build scripts and code transformations, doing some evaluation at build time—it is **NOT** suitable for handling arbitrary untrusted user input. Malicious user input _can_ execute arbitrary code.
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# example
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``` js
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var evaluate = require('static-eval');
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var parse = require('esprima').parse;
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var src = process.argv[2];
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var ast = parse(src).body[0].expression;
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console.log(evaluate(ast));
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```
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If you stick to simple expressions, the result is statically analyzable:
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```
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$ node '7*8+9'
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65
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$ node eval.js '[1,2,3+4*5-(5*11)]'
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[ 1, 2, -32 ]
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```
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but if you use statements, undeclared identifiers, or syntax, the result is no
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longer statically analyzable and `evaluate()` returns `undefined`:
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```
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$ node eval.js '1+2+3*n'
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undefined
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$ node eval.js 'x=5; x*2'
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undefined
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$ node eval.js '5-4*3'
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-7
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```
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You can also declare variables and functions to use in the static evaluation:
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``` js
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var evaluate = require('static-eval');
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var parse = require('esprima').parse;
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var src = '[1,2,3+4*10+n,foo(3+5),obj[""+"x"].y]';
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var ast = parse(src).body[0].expression;
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console.log(evaluate(ast, {
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n: 6,
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foo: function (x) { return x * 100 },
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obj: { x: { y: 555 } }
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}));
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```
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# methods
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``` js
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var evaluate = require('static-eval');
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```
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## evaluate(ast, vars={})
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Evaluate the [esprima](https://npmjs.org/package/esprima)-parsed abstract syntax
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tree object `ast` with an optional collection of variables `vars` to use in the
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static expression resolution.
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If the expression contained in `ast` can't be statically resolved, `evaluate()`
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returns undefined.
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# install
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With [npm](https://npmjs.org) do:
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```
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npm install static-eval
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```
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# license
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MIT
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