检查第一个字符串字符串 [英] Check First Char In String

问题描述

我有输入框。我正在寻找一种方法来启动 alert（）如果给定字符串的第一个字符等于'/'...。

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!' );

}

这是我目前的代码。它不起作用，我认为这是因为浏览器不知道何时检查该字符串......每当用户输入'/'作为第一个字符时，我都需要提醒。

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.

推荐答案

试试这个：

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

      alert( 'Boom!' );

    }
})

小提琴： http://jsfiddle.net/maniator/FewgY/

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