Javascript 的 left() , right(), leftField(), rightField() 函數

var str="Hello world!"
document.write("<br/>"+left(str,3));
document.write("<br/>"+right(str,4));
document.write("<br/>"+leftField(str,"e"));
document.write("<br/>"+rightField(str,"e"));

Output:

-----------------------------

Hel
rld!
H
llo world!   

函數 source code 如下:

-----------------------------

function trim(stringToTrim)

{

    if(stringToTrim.length>0){

        return stringToTrim.replace(/^\s+|\s+$/g,"");

    }

}

function left(str, num)

{

    return str.substring(0,num)

}

function right(str, num)

{

    return str.substring(str.length-num,str.length)

}

function leftField(str,delimit)

{

    var returnValue=str;

    var indexNumber=str.indexOf(delimit);

    if(indexNumber>=0){

        returnValue = str.substring(0,str.indexOf(delimit))

    }

    return returnValue;

}

function rightField(str,delimit)

{

    var returnValue=str;

    var indexNumber=str.indexOf(delimit);

    if(indexNumber>=0){

        returnValue = str.substring(indexNumber+delimit.length,str.length)

    }

    return returnValue;

}


說明:
leftField + rightField, 取文字裡特定分隔符號的左邊, 和右邊.