如何推回javascript上的按钮？
[英]How to push back the button on javascript?
问题描述
I start to learn javascript from W3scholl .
我开始从W3scholl学习 javascript。 I wanna make the push button from this tutorial :我想制作本教程中的按钮：
<html>
<body>
<h1>My First JavaScript</h1>
<button type="button"
onclick="document.getElementById('demo').innerHTML = Date()">
Click me to display Date and Time.</button>
<p id="demo"></p>
</body>
</html>
I want to clear the date text after I push the button again, how to do this?再次按下按钮后，我想清除日期文本，该怎么做？
2 个解决方案
解决方案1
0 2017-01-17 08:55:41
You could add a new button like this:您可以添加一个新按钮，如下所示：
<!DOCTYPE html>
<html>
<body>
<h1>My First JavaScript</h1>
<button type="button" onclick="document.getElementById('demo').innerHTML = Date()">
Click me to display Date and Time.
</button>
<button type="button" onclick="Empty()">
Click me to delete Date and Time.
</button>
<script>
function Empty(){
document.getElementById('demo').innerHTML = "";
}
</script>
<p id="demo"></p>
</body>
</html>
解决方案2
0 已采纳 2017-01-17 09:05:29
You could introduce a global variable state and save the last changed state.您可以引入全局变量state并保存最后更改的状态。
Click on button calls toggle and the function evaluates state for the next action.单击按钮调用toggle ，该函数评估下一个操作的state 。 At the end of the function state changes with the logical NOT !在函数结束时， state随着逻辑 NOT发生变化! . .
function toggle() { if (state) { // check state document.getElementById('demo').innerHTML = ''; document.getElementById('button1').innerHTML = 'Click me to display Date and Time.' } else { document.getElementById('demo').innerHTML = Date(); document.getElementById('button1').innerHTML = 'Delete Date and Time.' } state = !state; // toggle state } var state; // undefined, becomes later true and false
<button id="button1" type="button" onclick="toggle()">Click me to display Date and Time.</button> <p id="demo"></p>
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