如何将输入框中键入的文本转换为小写？

Question

我不知道如何将键入到文本输入框（txtQuestion）的文本转换为全部小写，即键入“ input”或“ INpUt”将被读取并输出相同的结果。

Answer 1

Use toLowerCase() function. Eg: "INPuT".toLowerCase();

 exampleFunction = function(){ //First we get the value of input var oldValue = document.getElementById('input').value; //Second transform into lowered case var loweredCase = oldValue.toLowerCase(); //Set the new value of input document.getElementById('input').value = loweredCase; } 

 <input id="input" type="text" onkeyup="exampleFunction()" /> 

Answer 2

You have to choose the events that you want to watch and then return to the input the same value but lowercase:

 function InputLowerCaseCtrl(element, event) { console.log(element.value) return element.value = (element.value || '').toLowerCase(); }; InputLowerCaseCtrl.bindTo = ['blur'].join(' '); document.addEventListener('DOMContentLoaded', function() { var input = document.querySelector('.input-lowercase'); return input.addEventListener(InputLowerCaseCtrl.bindTo, InputLowerCaseCtrl.bind(this, input)); }); 

 <input class="input-lowercase" type="text" /> 

Answer 3

You can convert any string input to lowercase using the String.prototype.toLowerCase function

https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/String/toLowerCase

For you example with an input for txtQuestion.

 var inputStringLowerCase = inputTxtQuestion.value.toLowerCase(); 

https://jsfiddle.net/fbkq2po4/