Let's say I have a paragraph that says 55+5. I want to have JavaScript return everything before the plus. Is this possible using substrings?
Yes. Try the String.split method: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/split
split() returns an array of strings, split by the character you pass to it (in your case, the plus). Just use the first element of the array; it will have everything before the plus:
const string = "foo-bar-baz"
const splittedString = string.split('-')
//splittedString is a 3 element array with the elements 'foo', 'bar', and 'baz'
