如何在JavaScript中检查输入是否为空? [英] How can I check if the input is empty in JavaScript?
本文介绍了如何在JavaScript中检查输入是否为空?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试制作阶乘计算器。如何检查输入是否为空?我试过'null'。但它没有用,或者我无法正常使用它。
b $ b b抱歉这个愚蠢的问题。我是新手 JavaScript
I am trying to make a factorial calculator. How can I check if the input is empty or not? I tried 'null'. But it didn't work or I couldn't use it properly.
sorry for the stupid question. I am newbie in JavaScript
function myFriday() {
var input = document.getElementById("input1").value;
var ever = function () {
if( !(isNaN(input))) {
var result = 1;
for(var i = 1; i <= input; i++ ) {
result = result * i
}
return result;
}
else if (input == null){
return "Please input a number"
}
else{
return "Please input a number"
}
}
document.getElementById("input2").value = ever();
}
<p>Input: <input type="text" id = "input1" /></p>
<p>Input: <input type="text" id = "input2" /></p>
<button onclick = "myFriday()">Calculate</button>
<p >RESULT: <span id = "result" style = "color:red"></span> </p>
推荐答案
function myFriday() {
var input = document.getElementById("input1").value;
var ever = function() {
if (input.trim() == '') {
return "Please input a number"
} else if (!(isNaN(input))) {
var result = 1;
for (var i = 1; i <= input; i++) {
result = result * i
}
return result;
}
}
document.getElementById("input2").value = ever();
}
<p>Input:
<input type="text" id="input1" />
</p>
<p>Input:
<input type="text" id="input2" />
</p>
<button onclick="myFriday()">Calculate</button>
<p>RESULT: <span id="result" style="color:red"></span>
</p>
这篇关于如何在JavaScript中检查输入是否为空?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
查看全文