JS正则表达式 替换括号,尖括号等

function toTxt(str) {  
    var RexStr = /\<|\>|\"|\‘|\&/g  
    str = str.replace(RexStr, function(MatchStr) {  
        switch (MatchStr) {  
        case "<":  
            return "<";  
            break;  
        case ">":  
            return ">";  
            break;  
        case "\"":  
            return """;  
            break;  
        case "‘":  
            return "‘";  
            break;  
        case "&":  
            return "&";  
            break;  
        default:  
            break;  
        }  
    })  
    return str;  
}