为什么onchange事件不起作用
[英]why onchange event doesn't work
问题描述
Why the onchange event doesn't work? 
为什么onchange事件不起作用？ below is my code: The php file is normally now problem. 下面是我的代码：php文件现在通常是问题。 because when i navigate to an other number with de input tag only, it works. 因为当我导航到仅带有de input标签的其他数字时，它可以工作。 But when i navigate with the four buttons it doesn't work. 但是当我用四个按钮导航时，它不起作用。 thank you for response! 谢谢您的回应！
<script>
function splus() {
document.getElementById("scene").value++;
document.getElementById("take").value="1";
}
function smin() {
if(document.getElementById('scene').value >1){
document.getElementById("scene").value--;}
}
function tplus() {
document.getElementById("take").value++;
document.getElementById('comment').value = '';
}
function tmin() {
if(document.getElementById('take').value >1){
document.getElementById("take").value--;}
}
function change(scene,take) {
if (window.XMLHttpRequest) {
// code for IE7+, Firefox, Chrome, Opera, Safari
xmlhttp = new XMLHttpRequest();
} else {
// code for IE6, IE5
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
document.getElementById("comment").innerHTML = xmlhttp.responseText;
}
};
xmlhttp.open("GET","selectst.php?scene="+scene+"&take="+take,true);
xmlhttp.send();
}
</script>
<body>
<button onclick="splus()" id="scene+">scene+</button>
<button onclick="smin()" id="scene-">scene-</button>
<button onclick="tplus()" id="take+">take+</button>
<button onclick="tmin()" id="take-">take-</button>
<input id="scene" type="number" onchange="change(this.value,document.getElementById('take').value)" value="1">
<input id="take" type="number" onchange="change(document.getElementById('scene').value,this.value)" value="1">
<textarea id="comment" rows="4" cols="50" placeholder="comments..."></textarea>
</body>
3 个解决方案
解决方案1
0 2015-11-17 14:29:37
This is because change event is fired only if there was an interaction with the element. 这是因为仅当与元素发生交互时才会触发change事件。 If you change element's value from javascript, it does not fires it and you will have to fire change event manually. 如果您从javascript更改元素的值，则不会触发它，您将不得不手动触发change事件。 You can refer following [MDN - post]/( https://developer.mozilla.org/en-US/docs/Web/Events/change ) for reference 您可以参考以下[MDN-post] /（https://developer.mozilla.org/en-US/docs/Web/Events/change ）以供参考
解决方案2
0 2015-11-17 14:33:14
Here's a workaround. 这是一种解决方法。 I am using onfocus(). 我正在使用onfocus（）。
function splus() { document.getElementById("scene").value++; document.getElementById("take").value = "1"; document.getElementById("scene").focus(); } function smin() { if (document.getElementById('scene').value > 1) { document.getElementById("scene").value--; } document.getElementById("scene").focus(); } function tplus() { document.getElementById("take").value++; document.getElementById('comment').value = ''; document.getElementById("take").focus(); } function tmin() { if (document.getElementById('take').value > 1) { document.getElementById("take").value--; } document.getElementById("take").focus(); } function change(scene, take) { alert("Clicked"); if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp = new XMLHttpRequest(); } else { // code for IE6, IE5 xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange = function() { if (xmlhttp.readyState == 4 && xmlhttp.status == 200) { document.getElementById("comment").innerHTML = xmlhttp.responseText; } }; xmlhttp.open("GET", "selectst.php?scene=" + scene + "&take=" + take, true); xmlhttp.send(); }
<button onclick="splus()" id="scene+">scene+</button> <button onclick="smin()" id="scene-">scene-</button> <button onclick="tplus()" id="take+">take+</button> <button onclick="tmin()" id="take-">take-</button> <input id="scene" type="number" onfocus="change(this.value,document.getElementById('take').value)" value="1"> <input id="take" type="number" onfocus="change(document.getElementById('scene').value,this.value)" value="1"> <textarea id="comment" rows="4" cols="50" placeholder="comments..."></textarea>
解决方案3
0 2015-11-17 14:34:36
With this solution : https://stackoverflow.com/a/2856602/5546267 使用此解决方案： https : //stackoverflow.com/a/2856602/5546267
function tplus() { document.getElementById("take").value++; if ("createEvent" in document) { var evt = document.createEvent("HTMLEvents"); evt.initEvent("change", false, true); document.getElementById("take").dispatchEvent(evt); } else document.getElementById("take").fireEvent("onchange"); }
<input onchange="alert('change !')" id="take" value="1"><br> <button onclick="tplus()">run</button>
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