// Main
(() => {
window.onload = () => {
const nativeConsoleLogFunc = window.console.error
window.console.error = (...data) => { // Override native function, just for test.
const range = document.createRange()
const frag = range.createContextualFragment(`<div>${data}</div>`)
document.querySelector("body").append(frag)
nativeConsoleLogFunc(...data)
}
// Add Enter event
document.querySelector(`input`).onkeyup = (keyboardEvent) => {
if (keyboardEvent.key === "Enter") {
const result = Parse(document.getElementById('expr').value)
if (result !== undefined) {
alert(result)
}
}
}
const testArray = [
// Basic Test
["(3+5)*4", ""],
["123.45+3*22*4", ""],
["8%2", ""],
["8%3", ""],
["7/3", ""],
["2*pi*e", 2 * Math.atan2(0, -1) * Math.exp(1)],
["2**3", ""],
// unary
["3+(-5)", ""],
["3+(+5)", ""],
// Function Test
["pow{2,3}*2", 16],
["4*sqrt{16}", 16],
["round{3.4}", 3],
["round{3.5}", 4],
["((1+e)*3/round{3.5})%2", ((1 + Math.exp(1)) * 3 / Math.round(3.5)) % 2],
["round{3.5}+pow{2,3}", Math.round(3.5) + Math.pow(2, 3)],
// error test
["21+", ValueMissingError],
["21+*", ParseError],
["(1+2", ParseError], // miss ")"
["round(3.12)", MissingParaError], // should be round{3.12}
["help", UnknownVarError],
]
for (let [testString, expected] of testArray) {
if (expected === "") {
expected = eval(testString) // Why don't you use eval instead of writing the function yourself? Because the browser may disable eval due to policy considerations. [CSP](https://content-security-policy.com/)
}
const actual = Parse(testString, false)
if (actual !== expected) {
if (actual instanceof Error && actual instanceof expected) {
continue
}
console.error(`${testString} = ${actual}, value <code>${expected}</code> expected`)
}
}
}
})()
// Script
class UnknownVarError extends Error {
}
class ValueMissingError extends Error {
}
class ParseError extends Error {
}
class MissingParaError extends Error {
}
/**
* @description Operator
* @param {string} sign "+", "-", "*", "/", ...
* @param {number} precedence
* @param {"L"|"R"} assoc associativity left or right
* @param {function} exec
* */
function Op(sign, precedence, assoc, exec = undefined) {
this.sign = sign
this.precedence = precedence
this.assoc = assoc
this.exec = exec
}
const OpArray = [
new Op("+", 10, "L", (l, r) => l + r),
new Op("-", 10, "L", (l, r) => l - r),
new Op("*", 20, "L", (l, r) => l * r),
new Op("/", 20, "L", (l, r) => l / r),
new Op("%", 20, "L", (l, r) => l % r),
new Op("**", 30, "R", (l, r) => Math.pow(l, r))
]
const VarTable = {
e: Math.exp(1),
pi: Math.atan2(0, -1), // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/atan2
pow: (x, y) => Math.pow(x, y),
sqrt: (x) => Math.sqrt(x),
round: (x) => Math.round(x),
}
/**
* @param {Op} op
* @param {Number} value
* */
function Item(op, value = undefined) {
this.op = op
this.value = value
}
class Stack extends Array {
constructor(...items) {
super(...items)
this.push(new Item(new Op("", 0, "L")))
}
GetLastItem() {
return this[this.length - 1] // fast then pop // https://stackoverflow.com/a/61839489/9935654
}
}
function Cursor(str, pos) {
this.str = str
this.pos = pos
this.MoveRight = (step = 1) => {
this.pos += step
}
this.PeekRightChar = (step = 1) => {
return this.str.substring(this.pos, this.pos + step)
}
/**
* @return {Op}
* */
this.MoveToNextOp = () => {
const opArray = OpArray.sort((a, b) => b.precedence - a.precedence)
for (const op of opArray) {
const sign = this.PeekRightChar(op.sign.length)
if (op.sign === sign) {
this.MoveRight(op.sign.length)
return op
}
}
return null
}
}
/**
* @param {Cursor} cursor
* */
function parseVal(cursor) {
let startOffset = cursor.pos
const regex = /^(?<OpOrVar>[^\d.])?(?<Num>[\d.]*)/g
const m = regex.exec(cursor.str.substr(startOffset))
if (m) {
const {groups: {OpOrVar, Num}} = m
if (OpOrVar === undefined && Num) {
cursor.pos = startOffset + Num.length
if (cursor.pos > startOffset) {
return parseFloat(cursor.str.substring(startOffset, startOffset + cursor.pos - startOffset)) // do not use string.substr() // It will be removed in the future. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Deprecated_and_obsolete_features#string_methods
}
}
if ("+-(".indexOf(OpOrVar) !== -1) {
cursor.pos++
switch (OpOrVar) {
case "+": // unary plus, for example: (+5)
return parseVal(cursor)
case "-":
return -(parseVal(cursor))
case "(":
const value = parseExpr(cursor)
if (cursor.PeekRightChar() === ")") {
cursor.MoveRight()
return value
}
throw new ParseError("Parsing error: ')' expected")
}
}
}
// below is for Variable or Function
const match = cursor.str.substring(cursor.pos).match(/^[a-z_][a-z0-9_]*/i) // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/match
if (match) {
// Variable
const varName = match[0]
cursor.MoveRight(varName.length)
const bracket = cursor.PeekRightChar(1)
if (bracket !== "{") {
if (varName in VarTable) {
const val = VarTable[varName]
if (typeof val === "function") {
throw new MissingParaError(`${varName} is a function, it needs big curly brackets`)
}
return val
}
}
// is function
const regex = /{(?<Para>[^{]*)}/gm
const m = regex.exec(cursor.str.substring(cursor.pos))
if (m && m.groups.Para !== undefined) {
const paraString = m.groups.Para
const para = paraString.split(',')
cursor.MoveRight(paraString.length + 2) // 2 = { + }
return VarTable[varName](...para)
}
throw new UnknownVarError(`unknown variable ${varName}`)
}
// Handle Error
if (cursor.str.length === cursor.pos) { // example: 1+2+
throw new ValueMissingError(`Parsing error at end of string: value expected.`)
} else { // example: 1+2+*
throw new ParseError("Parsing error: unrecognized value")
}
}
/**
* @param {string|Cursor} expr
* */
function parseExpr(expr) {
const stack = new Stack()
const cursor = (expr instanceof Cursor) ? expr : new Cursor(expr, 0)
while (1) {
let rightValue = parseVal(cursor)
const op = cursor.MoveToNextOp() ?? new Op("", 0, "L")
while (
op.precedence < stack.GetLastItem().op.precedence ||
(op.precedence === stack.GetLastItem().op.precedence && op.assoc === 'L')) {
const lastItem = stack.pop()
if (!lastItem.op.exec) { // end reached
return rightValue
}
rightValue = lastItem.op.exec(lastItem.value, rightValue)
}
stack.push(new Item(op, rightValue))
}
}
function Parse(str, alertError = true) {
try {
return parseExpr(str.replaceAll(" ", ""))
} catch (e) {
if (alertError) {
alert(e.message)
return undefined
}
return e
}
}
<input type="text" id="expr" name="expr" placeholder="123.45+3*22*4">
<button onclick="const x = Parse(document.getElementById('expr').value); if(x != null) alert(x);">
Calculate!
</button>
