检查字符串中的第一个字符

Question

I have input-box. I'm looking for a way to fire-up alert() if first character of given string is equal to '/'...

var scream = $( '#screameria input' ).val();

if ( scream.charAt( 0 ) == '/' ) {

  alert( 'Boom!' );

}

It's my code at the moment. It doesn't work and I think that it's because that browser doesn't know when to check that string... I need that alert whenever user inputs '/' as first character.

Answer 1

Try this out:

$( '#screameria input' ).keyup(function(){ //when a user types in input box
    var scream = this.value;
    if ( scream.charAt( 0 ) == '/' ) {

      alert( 'Boom!' );

    }
})

Fiddle: http://jsfiddle.net/maniator/FewgY/

Answer 2

You need to add a keypress (or similar) handler to tell the browser to run your function whenever a key is pressed on that input field:

var input = $('#screameria input');
input.keypress(function() {
  var val = this.value;
  if (val && val.charAt(0) == '/') {
    alert('Boom!');
  }
});