function handleTextNode(textNode) {
    if(textNode.nodeName !== '#text'
        || textNode.parentNode.nodeName === 'SCRIPT' 
        || textNode.parentNode.nodeName === 'STYLE'
    ) {
        //Don't do anything except on text nodes, which are not children 
        //  of  or .
        return;
    }
    
    
var find = ["build", "add", "Fast"];
var replace = ["Develope", "add", "Fast"];
let origText = textNode.textContent;
let newHtml = origText.replace(new RegExp("(" + find.map(function(i){return i.replace(/[.?*+^$[\]\\(){}|-]/g, "\\$&")}).join("|") + ")", "g"),function(s){ return replace[ find.indexOf(s)]});
     
    if( newHtml !== origText) {
        let newSpan = document.createElement('span');
        newSpan.innerHTML = newHtml;
        textNode.parentNode.replaceChild(newSpan,textNode);
    }
    // <span title="Dyslexia is a learning disorder that involves difficulty reading due to problems identifying speech sounds. " style="background-color: yellow"></span>
}

let textNodes = [];
//Create a NodeIterator to get the text nodes in the body of the document
let nodeIter = document.createNodeIterator(document.body,NodeFilter.SHOW_TEXT);
let currentNode;
//Add the text nodes found to the list of text nodes to process.
while(currentNode = nodeIter.nextNode()) {
    textNodes.push(currentNode);
}
//Process each text node
textNodes.forEach(function(el){
    handleTextNode(el);
});