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js 控制输入文字的字数

2017-06-02 14:57 218 查看

直接上代码。

<html>
<head>

</head>
<body>
<textarea id='txtArea' cols='50' rows='10'></textarea>
</body>
<script>

function getSelectionText() {
var selText = "";
if (window.getSelection) {  // 只有IE6,IE7,IE8不支持
var sel = document.activeElement;
if (sel &&
(sel.tagName.toLowerCase() == "textarea" ||
(sel.tagName.toLowerCase() == "input" &&
sel.getAttribute("type").toLowerCase() == "text")))
{
var text = sel.value;
selText = text.substring(
sel.selectionStart,
sel.selectionEnd
);
}
else {
var selRange = window.getSelection();
selText = selRange.toString();
}
} else {
if (document.getSelection) {  // 只有IE6,IE7,IE8,Firefox不支持. 代?并不会?行到?个分支
range = document.getSelection();
selText = range.toString();
} else if (document.selection.createRange) { // 只有IE6~10支持
var range = document.selection.createRange();
selText = range.text;
}
}
return selText;
}

function SetTextAreaMaxLength(controlId, length) {
// JScript File for TextArea
// Keep user from entering more than maxLength characters
function doKeypress(control, length) {
maxLength = length;
value = control.value;
if (maxLength && value.length > maxLength - 1) {
event.returnValue = false;
maxLength = parseInt(maxLength);
}
}
// Cancel default behavior
function doBeforePaste(control, length) {
maxLength = length;
if (maxLength) {
event.returnValue = false;
}
}
// Cancel default behavior and create a new paste routine 粘贴这一块，只有IE有效，其他浏览器不支持window.clipboardData
function doPaste(control, length) {

maxLength = length;
value = control.value;
if(maxLength){
event.returnValue = false;
maxLength = parseInt(maxLength);
var oTR = control.document.selection.createRange();
var iInsertLength = maxLength - value.length + oTR.text.length;
var sData = window.clipboardData.getData("Text").substr(0,iInsertLength);
oTR.text = sData;

}

function doDragenter(control, length) {
maxLength = length;
value = control.value;
if (maxLength) {
event.returnValue = false;
}
}
function addEvent(elm, evType, fn, useCapture) {
if (elm.addEventListener) {
elm.addEventListener(evType, fn, useCapture);
return true;
} else if (elm.attachEvent) {
var r = elm.attachEvent('on' + evType, fn);
return r;
} else {
elm['on' + evType] = fn;
}
}
function AttacheventTextAreaBeforePaste(obj, length) {
return function() {
doBeforePaste(obj, length)
}
}
function AttacheventTextAreaPaste(obj, length) {
return function() {
doPaste(obj, length)
}
}
function AttacheventTextAreaKeyPress(obj, length) {
return function() {
doKeypress(obj, length)
}
}
function AttacheventTextAreaDragEnter(obj, length) {
return function() {
doDragenter(obj, length);
}
}
var obj = document.getElementById(controlId);
addEvent(obj, 'keypress', AttacheventTextAreaKeyPress(obj, length), null);
addEvent(obj, 'beforepaste', AttacheventTextAreaBeforePaste(obj, length), null);
addEvent(obj, 'paste', AttacheventTextAreaPaste(obj, length), null);
addEvent(obj, 'dragenter', AttacheventTextAreaDragEnter(obj, length), null);
}

SetTextAreaMaxLength('txtArea',10);
</script>
</html>

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