@marvintau/arith-expr v0.0.9

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Simple Arithmetic Expression Evaluator

It supports validating and evaluating the arithmetic operation between integer, real number and variables given by a plain JS object. The working part is a parser generated from PEG.js. It's basically same to the simplest example PEG.js (found here), with some minor feature added.

You may use this module to avoid the usage of eval() in some circumstances. eval() is simple, but sometimes too simple. You may want to validate an expression without actually evaluate it. And using eval will really bring you some security concerns.

简单的算数运算求值。你可以用它来验证一个字符串是否是一个算数表达式。它支持 基本的整数和实数的四则运算。你还能传入一个变量表参数，然后让变量参与到运算中。 它背后是一个用PEG.js生成的parser。原理非常简单，几乎同这里 的示例程序是一样的。

这个组件的意义可能主要在于帮助你避免一部分eval()的使用。eval()有些简单粗暴， 有的时候你需要的是判断一个表达式是否合法，而并不想通过对它求值后的结果来判断。 而且eval除了求值的结果也不能给你更多额外的信息。此外eval也会带来安全隐患。

E.g

const parse = require('arith-expr');


console.log(parse('1+1'));
// will get you 2.

console.log(parse('3 * (5 - 2)'));
// will get you 9;

console.log(parse('3 * 1.5'));
// 4.5

console.log(parse('3 + b / c', {b: 1, c:0.5}))
//5

console.log(parse('function(){}'))
// throws SyntaxError, 'identifier [function] not found ...' ;

console.log(parse('<>'))
// throws SyntaxError, 'Expected '(', but found ...';