make search case insnesitive

How do I add the case insensitive search?

function getPhrases(){
		var searchChapWords=document.getElementsByName('search_chap_words'); //grabs from the 1st column
		var searchChapWords2=document.getElementsByName('search_chap_words2'); //grabs from the 2nd column
		document.getElementById('keyword0').innerHTML = "";
		document.getElementById('keyword1').innerHTML = "";
		
		var myOldString = "";
		var myOldString2 = "";
		for(i=0;i<searchChapWords.length;i++){
			myOldString += searchChapWords[i].innerHTML + " "; //joins 1st column in one string
		}
		for(i=0;i<searchChapWords2.length;i++){
			myOldString2 += searchChapWords2[i].innerHTML + " "; //joins 2nd column in one string
		}
	var myNewString = myOldString.replace(/[\:\;\?\.\,\(\)\']/gi, "");//to eliminate the punctuations
	var myNewString2 = myOldString2.replace(/[\:\;\?\.\,\(\)\']/gi, "");//to eliminate the punctuations
	
	var mySplitString = myNewString.split(" ");
	var mySplitString2 = myNewString2.split(" ");
	
	// Our common phrase goes here.
	var common_phrase = "";
	var phraseCollection =  new Array();
	// Now go through a double-loop and match each common word.
	//for(k=0; k<15; k++){
		k=0;
		phraseCollection[k] = "";
		for(var i=0; i < mySplitString.length; i++){ //length of 1st array
			if(i!=0){
				//common_phrase += " ";
				phraseCollection[k] += "";
			}
			for(var j=0; j < mySplitString2.length; j++){ //picks a word and runs through 2nd array
				if(mySplitString[i] == mySplitString2[j]){ //when match found
					phraseCollection[k] += mySplitString[i]+" "; //records word
					// Move it forward to the next word in the phrase1.
					i++; // goes to the next word
				}
			}
			k++;//skips to the next array element
			phraseCollection[k]="";
		}
	//}
	function sortNumber(a,b){
		return a - b;
	}
	var sortByLength = new Array();
	
	for(m=0; m<sortByLength.length; m++){
		sortByLength[m] = phraseCollection[m].length;

	}	
	for(k=0; k<phraseCollection.length; k++){
		if(phraseCollection[k].length> document.getElementById("number_words").value){
			common_phrase += phraseCollection[k] + ",,";
		}		
	}
	// Clean up the extra space at the end.
	common_phrase = common_phrase.substr(0, common_phrase.length-1);
	document.getElementById('keyword0').innerHTML=common_phrase;

}

Code (markup):

 

change

var mySplitString = myNewString.split(" ");
var mySplitString2 = myNewString2.split(" ");

Code (markup):

to

var mySplitString = myNewString.toLowerCase().split(" ");
var mySplitString2 = myNewString2.toLowerCase().split(" ");

Code (markup):

untested, but i think it should work.