javascript javascript防止复制/粘贴超出textarea中的字符限制
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javascript prevent copy/pasting beyond character limit in textarea
提问by Brian Phillips
I have the following code (pulled from this question) for setting a character limit on textareas.
我有以下代码（从这个问题中提取）用于在 textareas 上设置字符限制。
function maxLength(el) {
if (!("maxLength" in el)) {
var max = el.attributes.maxLength.value;
el.onkeypress = function () {
if (this.value.length >= max) return false;
};
}
}
var maxtext = document.getElementsByClassName("maxtext");
for (var i = 0; i < maxtext.length; i++) {
maxLength(maxtext[i]);
}
And an example of my html for textareas:
以及我的 textareas html 示例：
<textarea maxlength="150" class="maxtext"></textarea>
This all works just fine in Firefox and Chrome. In IE7+, it will stop me if I type up to the limit, but I'm then able to copy/paste text without restriction.
这一切在 Firefox 和 Chrome 中都可以正常工作。在 IE7+ 中，如果我输入到限制，它会阻止我，但我可以不受限制地复制/粘贴文本。
Any way to modify this script to prevent copy/pasting beyond the max character limit?
有什么方法可以修改此脚本以防止复制/粘贴超出最大字符数限制？
回答by Chase
Listen for the onpasteevent. Once the event fires, grab the text from the clipboardand manipulate it how you like.
监听onpaste事件。事件触发后，从剪贴板中抓取文本并按照您的喜好对其进行操作。
HTML
HTML
<textarea id="test" maxlength="10" class="maxtext"></textarea>
JAVASCRIPT
爪哇脚本
var test = document.getElementById("test");
test.onpaste = function(e){
//do some IE browser checking for e
var max = test.getAttribute("maxlength");
e.clipboardData.getData('text/plain').slice(0, max);
};
回答by Shuping
You could listen to the onchangeevent to check the content length, if exceeds the limit then subtract it.
您可以监听onchange事件以检查内容长度，如果超过限制则减去它。
