SearchSwitch/v3/background.js

function switchSearch(tab) {
    const bingSearch = "https://www.bing.com/search?q=";
    const googleSearch = "https://www.google.com/search?q=";

    const bingImageSearch = "https://www.bing.com/images/search?q="
    const googleImageSearchSubstring = "&tbm=isch";
    const url = tab.url;

    let newURL;
    let removeEngine;
    let searchEnd;
    let justSearch;
    //Handle bing searches
    if (url.substring(0, bingSearch.length) === bingSearch) {
        removeEngine = url.slice(bingSearch.length);
        searchEnd = removeEngine.indexOf('&');
        justSearch = removeEngine.substring(0, searchEnd);

        newURL = googleSearch + justSearch + '&';

    }
	//Handle Google image searches
	else if (url.indexOf(googleImageSearchSubstring) > googleSearch.length) {
		removeEngine = url.slice(googleSearch.length);
		searchEnd = removeEngine.indexOf('&');
		justSearch = removeEngine.substring(0, searchEnd);

		newURL = bingImageSearch + justSearch + '&';
	}
    //Handle Google searches
    else if (url.substring(0, googleSearch.length) === googleSearch) {
        removeEngine = url.slice(googleSearch.length);
        searchEnd = removeEngine.indexOf('&');
        justSearch = removeEngine.substring(0, searchEnd);

        newURL = bingSearch + justSearch + '&';
    }
    //Handle bing image searches
    else if (url.substring(0, bingImageSearch.length) === bingImageSearch) {
        removeEngine = url.slice(bingImageSearch.length)
        searchEnd = removeEngine.indexOf('&');
        justSearch = removeEngine.substring(0, searchEnd);

        newURL = googleSearch + justSearch + googleImageSearchSubstring + '&';
    }


    return newURL;
}

chrome.action.onClicked.addListener((tab) => {
        chrome.scripting.executeScript({
            target: {tabId: tab.id},
            func: switchSearch,
            args: [tab]
        }, async (redirect) => {
            await chrome.tabs.update({url: redirect[0].result});
        });
    }
)