防止单词之间超过一个空格

Question

I have a function that prevents people putting numbers or any symbol but letters onkeypress into a text box due to ongoing problems with data entry.

<td><input type="text" name="name" onkeypress="return isAlfa(event)"></td>

Now some staff for reasons unknown put two spaces between words at random times. So I need to prevent them putting more than one space between words. I want to do this in the same function, but it keeps breaking.

function isAlfa(evt) {
  evt = (evt || window.event);
  var charCode = (evt.which || evt.keyCode);

  if ((charCode > 32)
    && (charCode < 65 || charCode > 90)
    && (charCode < 97 || charCode > 122)
  ) {
    return false;
  }
  return true;
}

How can I prevent them entering more than one space between words?

Answer 1

Neglecting all the other helpful suggestions and comments and strictly following the OP's requirements one has to ...

1. Adapt the return condition in a way that takes into account if, with the current keystroke, a whitespace sequence is going to be created.
2. Thus one has to implement a method that determines exactly that.
3. There might be some possible helper methods too.
4. code example ...

 function isWhiteSpace(char) { return (/\\s/).test(char); } function willCreateWhitespaceSequence(evt) { var willCreateWSS = false; if (isWhiteSpace(evt.key)) { var elmInput = evt.currentTarget; var content = elmInput.value; var posStart = elmInput.selectionStart; var posEnd = elmInput.selectionEnd; willCreateWSS = ( isWhiteSpace(content[posStart - 1] || '') || isWhiteSpace(content[posEnd] || '') ); } return willCreateWSS; } function isAlfa(evt) { evt = (evt || window.event); var charCode = (evt.which || evt.keyCode); return (( (charCode > 32) && (charCode < 65 || charCode > 90) && (charCode < 97 || charCode > 122) ) || willCreateWhitespaceSequence(evt)) ? false : true; }

 <input type="text" name="name" onkeypress="return isAlfa(event)"/>

Answer 2

This code will prevent multiple white spaces, that is, it will only allow 1 space and it will prevent two or more white spaces. You can configure the amount of white space you want to deny.

Answer 3

Rather than listening for and evaluating each key press it would be far simpler just to react to any and all input and then sanitise whatever was entered via a RegExp.

Example:

<input type=text id=myfield />

JS:

document.querySelector('#myfield').addEventListener('input', evt => {
    evt.target.value = evt.target.value.replace(/[^a-z\s]/ig, '').replace(/\s{2,}/g, ' ');
});

That first replaces all non-letters and spaces with nothing, then replaces sequences of 2 or more spaces with a single space.

Answer 4

may be try to use something like this. on your keypress event try to check the last value by using string substr method and if that gives you a space and current code is also a Space then prevent or do whatever you want to do with input.

 function checkstuff(event){ if (event.target.value.substr(-1) === ' ' && event.code === 'Space') { console.log('space pressed in sequence'); } }

 <input type='text' onkeypress="checkstuff(event)">