ceval

Ceval

online demo;

零依赖，适合表达式运算;

No dependence, suitable for calculating expressions;

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│   Gzipped Size:  6.76 KB      │
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usage

npm i ceval -S

introduce

Options

const Parser = require('ceval')
const analysis = new Parser({
   /**
   * @desc Allow operators
   * @type {boolean}
   */
  endableOperators?: boolean = true;

  /**
   * @desc number enable multi bit base
   * @type {boolean}
   */
  endableBitNumber?: boolean = true;

  /**
   * @desc Allow access to members
   * @type {boolean}
   */
  allowMemberAccess?: boolean = true;

  /**
   * @desc Zoom in calculation allowed by default
   * @see To process the results of arithmetic e.g 0.1+0.2 !== 0.3  || 1.0-0.9 !== 0.1
   * Beyond the boundary（ta > Number.MAX_SAFE_INTEGER || ta < Number.MIN_SAFE_INTEGER）will not do processing, restore arithmetic
   * @requires false 
   * @type {boolean}
   */
  allowHandleNumberPrecision?: boolean = true;

  /**
   * @desc Operators are not allowed to be overridden by presetvalue by default
   * @see In some cases, developers want to make more accurate calculations, such as BigInt, presetValue={'+':Function}
   * @requires false
   * @type {boolean}
   * @memberof CevalOptions
   */
  allowOperatorsCovered?: boolean;

  /**
   * @desc Trigger default return value when there is no return value or undefined
   * @type {any}
   */
  defaultReturnValues?: any = '' // done
})

API

Parser Instance API

api	desc	type
operatorMap	Operators mapping table, which can be used in preset values overlay operation	Record<string, Function>
getSupportOperationMap	The name of the operator method supported by the query can be overridden	(ops: string) => null
parseString	Parsing strings, exposing methods to the outside world	(expression: string, values?: Record<string, any>) => any;
getCurrentValues	Get current datapool preset + external + internal declaration	() => Record<string, any>
updatePresetValues	Update PresetValues	(values: Record<string, any>) => void
updateOptions	Update Option	(Options: Partial) => void
getOptions	get Options	() => Readonly

about Options example test case;

use test262 test case;

rule

There are two rules:

Semicolon at the end

e.g.

parse('0b01 + 0b01;') // 2 

Although it is not necessary in a simple expression operation, but it's a good habit.The parser can know exactly where the end is, Although it doesn't have too many restrictions.

e.g.

parse(`
  function abs(a,b,c) { 
    let b = 1 /* ⚠️ error, must has semicolon */
    c = 2;
    return(a+b+c);
  };
  abs(3,4,8);
`)

statement

"var" statement does not affect "scope", it's inserted into values "let" and "const" assigned to the current scope, warn if the current scope exists

var Parser = require('ceval');

var instance = new Parser({/*...*/});
var parse = instance.parseString;

parse(`
  var obj = { foo:'foo', bar: 'bar'};

  function abs(a,b,c) {
    var d = 'global';
    return (a+b+c);
  }
  abs(1,2,3)
`)

console.log(instance.getCurrentValues().obj); // { foo:'foo', bar: 'bar'}
console.log(instance.getCurrentValues().d); // 'global'

parse(`
  let foo = 'foo';
  const bar = 'bar';
  function abs(a,b,c) {
    let d = 'scope';
    const e = 'scope';
    return (a+b+c);
  }
  abs(1,2,3)
`)
console.log(instance.getCurrentValues().foo); // undefined
console.log(instance.getCurrentValues().bar); // undefined
console.log(instance.getCurrentValues().d); // undefined
console.log(instance.getCurrentValues().e); // undefined

basic

const { parse: parse } = analysis

Number

parse('0b01') // 1
parse('0b11') // 3
parse('0b010101') // 21

parse('01') // 1
parse('077') // 63
parse('01111') // 585

parse('.1') // 1
parse('33') // 33
parse('100.00') // 100

parse('0x01') // 1
parse('0xaf') // 175
parse('0x9fac') // 40876

parse(`1e+308*2 === Infinity`) // true

parse(`
    var x = NaN;
    var y = NaN;
    return (x !== y);
  `) // true

parse(`
  var x = NaN;
  return(typeof(x) === 'number');
  `) // true

parse(`
  var x = NaN;
  var x_geq_0=(x >= 0.0);
  return(x_geq_0)
  `) // false

parse(`
  var x=+Infinity;
  return(typeof(x) === 'number')
  `) // true

More testcase here

calculation

const obj = `{ a: 1, b: 2, c: 3, d: { e: 4, f: 5}}`
parse(`1+1`);                       // 2
parse(`-1-2-3`);                    // -6
parse(`1*2*3`);                     // 6
parse(`1/2/4`);                     // 0.125
parse(`undefined || 2`);            // 2
parse(`~-1 || -2 || 3`);            // -2
parse(`-0 == +0`);                  // true
parse(`~1 > 1`);                    // false
parse(`false > false > 1`);         // false
parse(`5 >= 0`);                    // true
parse(`1 in [1, 2, 3]`);            // true
parse(`undefined in [1, 2, true]`); // false
parse(`'a' in ${obj}`);             // true
parse(`\'\'a\'\' in ${obj}`);       // true ('"a"'  === 'a') is Palindrome
parse(`1 === true`);                // false
parse(`3%2`);                       // 1

Function

parse(`
  function abs(a,b,c) { 
    var a = 5; /* => inject to presetValues */
    let b = 1; /* => inject to current scope */
    c = 2;
    const d = 4; /* If the current scope contains the variable D, It will trigger warning, but the operation will still be completed, is overlay */
    return(a+b+c);
  };
  abs(3,4,8);
`)

Object & Array

parse(`[1*2, false, true, undefined, null]`); // Array[]
parse(`var a = { b: { c: ['a','b','c','d']} };'e' in a.b.c`); // false
parse(`{ a: 1, b: 2, c: { d: undefined, e: { f: false, g: { h: null }}}}`); // object

parse(`var a = { b: 2 };a.b`) //2;
parse(`var a = { b: 2 };a["b"]`) //2;
parse(`var a = { b: 2, c:3 };var b='c';a[b]`) //3;

// data reference
parse(`
  var a = { b: 2, c:[1,2,3]};
  var b='c';
  a[b][0] = '0';
  return a[b];
`) // ['0',2,3]

parse(`
  var arr = [1,2,3];
  arr[0] = 0;
  return arr;
`) // [0,2,3]

Variable

parse(`
var a = { foo: 1 };
var b = { bar: 2 };
let a = { state: 1 } // ⚠️, Raise warning, current scope exists key
const b = { state: 1 } // ⚠️, Raise warning, current scope exists key

let c = { coo: 1} // success;
const d = { coo: 1} // success;
`)

parse(`
var a = { a: [false, true, undefined, null, ''] };
var b = { b: true, c: undefined, d:{ e: a, f: '1', g: {}}};
`) // Can be obtained from the instance. api: getCurrentValues

this

Operator

Through instance.operatorMap Get all operators；

return

return interrupt this operation cycle; but it doesn't affect the outside world.

parse(`
return 1;
return 2;
`) // 1

parse(`
  var foo = 'foo'
  function abs(a,b,c) {
    return a;
    return b;
  }
  var bar = abs(1,2,3)
  return (bar + foo);
`) // foo1

Other

Please move to test case for more examples。

TODO: Test39 Some test cases,

speed of progress

2020-06-24 done: number, null, boolean

In more function extension, welcome to participate or propose feature.

development

develop

npm start

build

# webapck build umd module, No compression
npm run build:umd

# rollup build umd module, Compressed version
npm run build:rollup

# webpack build docs
npm run build:docs

publish

npm publish