From plain text to TEX - Javascript [closed] - node.js

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I'm building a math application and I want to show math formulas written with a good design in javascript (nodejs). So I would transorm plain text to TEX format.
From formula like this:
(25*5)/6
To formula like this:
\frac{(25 \cdot 5)}{6}
To good design:
If there are other known methods you advise me.
Many thanks in advance!

Answer 1

I've rewritten this expression parser from java to javascript. not the most straightforward way. Note that this is not extensively tested.
function texFromExpression(str){
var pos = -1, ch;
function nextChar(){
ch = (++pos < str.length) ? str.charAt(pos) : -1;
}
function eat(charToEat) {
while (ch == ' ') nextChar();
if (ch == charToEat) {
nextChar();
return true;
}
return false;
}
function parse(){
nextChar();
var x = parseExpression();
if (pos < str.length) throw `Unexpected: ${ch}`
return x;
}
function parseExpression() {
var x = parseTerm();
for (;;) {
if (eat('+')) x = `${x} + ${parseTerm()}` // addition
else if (eat('-')) x = `${x} - ${parseTerm()}` // subtraction
else return x;
}
}
function parseTerm() {
var x = parseFactor();
for (;;) {
if (eat('*')) x=`${x} \\cdot ${parseTerm()}`; // multiplication
else if (eat('/')) x= `\\frac{${x}}{${parseTerm()}}`; // division
else return x;
}
}
function parseFactor() {
if (eat('+')) return `${parseFactor()}`; // unary plus
if (eat('-')) return `-${parseFactor()}`; // unary minus
var x;
var startPos = pos;
if (eat('(')) { // parentheses
x = `{(${parseExpression()})}`
eat(')');
} else if ((ch >= '0' && ch <= '9') || ch == '.') { // numbers
while ((ch >= '0' && ch <= '9') || ch == '.') nextChar();
x = str.substring(startPos, pos);
} else if (ch >= 'a' && ch <= 'z') { // variables
while (ch >= 'a' && ch <= 'z') nextChar();
x= str.substring(startPos, pos);
if(x.length>1){
x = `\\${x} {${parseFactor()}}`;
}
} else {
throw `Unexpected: ${ch}`
}
if (eat('^')) x = `${x} ^ {${parseFactor()}}` //superscript
if(eat('_')) x = `${x}_{${parseFactor()}}`;
return x;
}
return `$${parse()}$`;
}