function init() {
    'use strict';
    let can = document.getElementById('canvas');
    let ctx = canvas.getContext('2d');
    resizeBlock(can, 50, 50);
    setCSS1('can', 'borderWidth', '20px');// function not working
    setCSS2('can', 'borderWidth', '20px');// also true function not working
}

function setCSS1(element, rule, value) {
    element.style.rule = value;
    return element; // should element return or not?
}

function setCSS2(element, rule, value) {
    element.style.rule = value;
    return element; // should element return or not?
}

window.onload = init;

function init() { ...snip... }
window.onload = init;