CODEWITHSUNDEEP
javascriptregexstring
user3787706
user3787706

Reputation: 659

Get last character in javascript string ignoring whitespace

Given string:

234 + (note the space after +)

I want to write a function that determines if there was one of certain characters there (in this case +)

Background

I have an input to hold a mathematics equation

I want to have buttons that can add 2-digit, 3-digit numbers etc. While also allowing the user to type in their own numbers and operators.

So if the input is empty, and the user clicks the 3-digit button, I want 234to be added to the input.

If he clicks again, I want to add + 234 (as there is no operator there)

Now, if the user types another + (optionally followed by any amount of spaces), I want to add only 234 again

tldr

How can i read the last non-whitespace character in a string? jquery preferred, vanilla is also ok.

Upvotes: 2

Views: 2662

Answers (3)

grabantot
grabantot

Reputation: 2149

https://regex101.com/r/zV5zV2/1

str = '234 +   \n 823 + sqrt(4)       \n 7880 - cos(16)\t'
re = /(\S)+(?=\s*$)/gm
lastWords = str.match(re)
console.log(lastWords)  //logs ["+", "sqrt(4)", "cos(16)"]

Input string is multiline to illustrate different possibilities.

Upvotes: 1

adeneo
adeneo

Reputation: 318192

First trim off any whitespace, then just get the last character and compare it to something

var str = "234 + ";

str = str.trim();

var last = str.charAt(str.length - 1);

Upvotes: 4

ndnenkov
ndnenkov

Reputation: 36101

.(?=\s*$)
  • . - a character
  • (?=) - positive lookahead to verify the existence of, but not include in the match
  • \s* - zero or more spaces
  • $ - til the end of the string

See it in action

Upvotes: 4

Related Questions