2.3、utils.js

function setProp(dom, key, value) {
    if (/^on/.test(key)) {
        dom[key.toLowerCase()] = value;
    } else if (key === 'style') {
        if (value) {
            for (let styleName in value) {
                if (value.hasOwnProperty(styleName)) {
                    dom.style[styleName] = value[styleName];
                }
            }
        }
    } else {
        dom.setAttribute(key, value);
    }
    return dom;
}
export function setProps(elem, oldProps, newProps) {
    for (let key in oldProps) {
        if (key !== 'children') {
            if (newProps.hasOwnProperty(key)) {
                setProp(elem, key, newProps[key]);
            } else {
                elem.removeAttribute(key);
            }
        }
    }
    for (let key in newProps) {
        if (key !== 'children') {
            setProp(elem, key, newProps[key])
        }
    }
}