正则表达式只允许单词之间有一个空格

Question

I'm trying to write a regular expression to remove white spaces from just the beginning of the word, not after, and only a single space after the word.

Used RegExp:

var re = new RegExp(/^([a-zA-Z0-9]+\s?)*$/);

Test Exapmle:

1) test[space]ing - Should be allowed 
2) testing - Should be allowed 
3) [space]testing - Should not be allowed 
4) testing[space] - Should be allowed but have to trim it 
5) testing[space][space] - should be allowed but have to trim it 

Only one space should be allowed. Is it possible?

Answer 1

To match, what you need, you can use

var re = /^([a-zA-Z0-9]+\s)*[a-zA-Z0-9]+$/;

Maybe you could shorten that a bit, but it matches _ as well

var re = /^(\w+\s)*\w+$/;

Answer 2

function validate(s) {
    if (/^(\w+\s?)*\s*$/.test(s)) {
        return s.replace(/\s+$/, '');
    }
    return 'NOT ALLOWED';
}
validate('test ing')    // => 'test ing'
validate('testing')     // => 'testing'
validate(' testing')    // => 'NOT ALLOWED'
validate('testing ')    // => 'testing'
validate('testing  ')   // => 'testing'
validate('test ing  ')  // => 'test ing'

BTW, new RegExp(..) is redundant if you use regular expression literal.

Answer 3

This one does not allow preceding and following spaces plus only one space between words. Feel free to add any special characters You want.

^([A-Za-z]+ )+[A-Za-z]+$|^[A-Za-z]+$

demo here

Answer 4

Working code- Inside my name.addTextChangedListener() :

public void onTextChanged(CharSequence s, int start, int before, int count) {
            String n = name.getText().toString();
            if (n.equals(""))
                name.setError("Name required");
            else if (!n.matches("[\\p{Alpha}\\s]*\\b") | n.matches(".*\\s{2}.*") | n.matches("\\s.*")) {
                if (n.matches("\\s.*"))
                    name.setError("Name cannot begin with a space");
                else if (n.matches(".*\\s{2}.*"))
                    name.setError("Multiple spaces between texts");
                else if (n.matches(".*\\s"))
                    name.setError("Blank space at the end of text");
                else
                    name.setError("Non-alphabetic character entered");
            }
        }

You could try adapting this to your code.

Answer 5

var f=function(t){return Math.pow(t.split(' ').length,2)/t.trim().split(' ').length==2}

f("a a")
true
f("a a ")
false
f("a  a")
false
f(" a a")
false
f("a a a")
false

Answer 6

Here is a solution without regular expression. Add this script inside document.ready function it will work.

var i=0;
        jQuery("input,textarea").on('keypress',function(e){
            //alert();
            if(jQuery(this).val().length < 1){
                if(e.which == 32){
                    //alert(e.which);
                return false;
                }   
            }
            else {
            if(e.which == 32){
                if(i != 0){
                return false;
                }
                i++;
            }
            else{
                i=0;
            }
            }
        });

Answer 7

const handleChangeText = text => {
    let lastLetter = text[text.length - 1];
    let secondLastLetter = text[text.length - 2];
    if (lastLetter === ' ' && secondLastLetter === ' ') {
      return;
    }
    setInputText(text.trim());
  };

Answer 8

use this

^([A-Za-z]{5,}|[\s]{1}[A-Za-z]{1,})*$

Demo:- https://regex101.com/r/3HP7hl/2