新浪操作textarea的工具函数

记事本 2011-01-18 22:17:25 浏览 2,823 次
标签 textarea
从新浪的库上copy下来的操作textarea的工具函数，用做学习研究目的。
App.TextareaUtils = (function () { 
    var it = {}, 
        ds = document.selection; 
    it.selectionStart = function (oElement) { 
        if (!ds) { 
            return oElement.selectionStart 
        } 
        var er = ds.createRange(), 
            value, len, s = 0; 
        var er1 = document.body.createTextRange(); 
        er1.moveToElementText(oElement); 
        for (s; er1.compareEndPoints("StartToStart", er) < 0; s++) { 
            er1.moveStart("character", 1) 
        } 
        return s 
    }; 
    it.selectionBefore = function (oElement) { 
        return oElement.value.slice(0, it.selectionStart(oElement)) 
    }; 
    it.selectText = function (oElement, nStart, nEnd) { 
        oElement.focus(); 
        if (!ds) { 
            oElement.setSelectionRange(nStart, nEnd); 
            return
        } 
        var c = oElement.createTextRange(); 
        c.collapse(1); 
        c.moveStart("character", nStart); 
        c.moveEnd("character", nEnd - nStart); 
        c.select() 
    }; 
    it.insertText = function (oElement, sInsertText, nStart, nLen) { 
        oElement.focus(); 
        nLen = nLen || 0; 
        if (!ds) { 
            var text = oElement.value, 
                start = nStart - nLen, 
                end = start + sInsertText.length; 
            oElement.value = text.slice(0, start) + sInsertText + text.slice(nStart, text.length); 
            it.selectText(oElement, end, end); 
            return
        } 
        var c = ds.createRange(); 
        c.moveStart("character", -nLen); 
        c.text = sInsertText 
    }; 
    it.getCursorPos = function (obj) { 
        var CaretPos = 0; 
        if ($IE) { 
            obj.focus(); 
            var range = null; 
            range = ds.createRange(); 
            var stored_range = range.duplicate(); 
            stored_range.moveToElementText(obj); 
            stored_range.setEndPoint("EndToEnd", range); 
            obj.selectionStart = stored_range.text.length - range.text.length; 
            obj.selectionEnd = obj.selectionStart + range.text.length; 
            CaretPos = obj.selectionStart 
        } else { 
            if (obj.selectionStart || obj.selectionStart == "0") { 
                CaretPos = obj.selectionStart 
            } 
        } 
        return CaretPos 
    }; 
    it.getSelectedText = function (obj) { 
        var selectedText = ""; 
        var getSelection = function (e) { 
            if (e.selectionStart != undefined && e.selectionEnd != undefined) { 
                return e.value.substring(e.selectionStart, e.selectionEnd) 
            } else { 
                return ""
            } 
        }; 
        if (window.getSelection) { 
            selectedText = getSelection(obj) 
        } else { 
            selectedText = ds.createRange().text 
        } 
        return selectedText 
    }; 
    it.setCursor = function (obj, pos, coverlen) { 
        pos = pos == null ? obj.value.length : pos; 
        coverlen = coverlen == null ? 0 : coverlen; 
        obj.focus(); 
        if (obj.createTextRange) { 
            var range = obj.createTextRange(); 
            range.move("character", pos); 
            range.moveEnd("character", coverlen); 
            range.select() 
        } else { 
            obj.setSelectionRange(pos, pos + coverlen) 
        } 
    }; 
    it.unCoverInsertText = function (obj, str, pars) { 
        pars = (pars == null) ? {} : pars; 
        pars.rcs = pars.rcs == null ? obj.value.length : pars.rcs * 1; 
        pars.rccl = pars.rccl == null ? 0 : pars.rccl * 1; 
        var text = obj.value, 
            fstr = text.slice(0, pars.rcs), 
            lstr = text.slice(pars.rcs + pars.rccl, text == "" ? 0 : text.length); 
        obj.value = fstr + str + lstr; 
        this.setCursor(obj, pars.rcs + (str == null ? 0 : str.length)) 
    }; 
    return it 
})();
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