Validation of a mathematical formula based on user input

javascript, jquery, math, regex

Solution

You may try something like this:

var re = /[^\]\d\(\)+\-*\/,.]+(?=[^\[\]\(\)]*(?:\[|\(|$))/g;
$("#inputID").keyup(function(){
    this.value = this.value.replace(re, "");
});

Keep in mind, though, that you have to be sure that the parenthetical structure is coherent with your syntax.

Advice: use RegExr to test your regular expressions, but remember that it's more powerful than Javascript regex support.

Problem

I know that SO is not a code generator, but I break my head and I'll got mad with this RegExp. I've `<input />` type text, in a HTML `<form />`. The input is automatically filled when the user double-click on elements in a specific list. This event will generate string like `"[text:number]"` or `"[text:number:text]"`, and place it at the cursor position in my `<input />` field. The first goal of this process is to construct a mathematic formula structure. I mean, the generated strings between brackets will insert elements, then I want to allow the user to put only numbers and operators. I've tried to bind the `keydown` event, and test the char with `String.fromCharCode(e.which);` but for the keys "+" or "-" (and other operators) this function returns alphabeticals chars. Without success. Then, I've finally decided to use the `keyup` event, then use a RegExp to replace the `<input />` value. ``` $("#inputID").keyup(function(){ var formule = $(this).val(); var valid_formule = formule.replace(CRAZY_REGEXP,''); $(this).val(valid_formule); }); ``` So, my question is as follows : How construct a javascript RegExp, to remove all chars which are not between brackets, and which are differents of `()+-*/,.` and `numbers`. An example : `"a[dse:1]a+a[dse:5]a+a[cat:5:sum]a+(a10a/5,5)!"` will become `"[dse:1]+[dse:5]-[cat:5:sum]+(10/5,5)"` I'm open to another way to achieve my goal if you have some ideas. Thanks !

Original source