QuickDirtyBionic.js

function bionicizeText(str) {
    let phrase = str.split(" ");
    let results = [];

    results.push(phrase.map(word => bionicizeWord(word)));

    return results.join(" ");

    function bionicizeWord(w) {
        let strong = document.createElement('strong');
        strong.textContent = w.slice(0, Math.ceil(w.length / 2));
        return strong.outerHTML + w.slice(Math.ceil(w.length / 2));
    }
}

bionicizeText("This is a test");

Saw one of those "bionic text" promotional posts on SM and thought it would make for an interesting distraction (i.e. coding challenge) to pass an otherwise stressful evening. Not meant to be taken seriously with .bold() etc obviously.

Updated to use createElement/strong instead.