snabbdom/build/modules/class.js

A virtual DOM library with focus on simplicity, modularity, powerful features and performance.

function updateClass(oldVnode, vnode) {
    let cur;
    let name;
    const elm = vnode.elm;
    let oldClass = oldVnode.data.class;
    let klass = vnode.data.class;
    if (!oldClass && !klass)
        return;
    if (oldClass === klass)
        return;
    oldClass = oldClass || {};
    klass = klass || {};
    for (name in oldClass) {
        if (oldClass[name] && !Object.prototype.hasOwnProperty.call(klass, name)) {
            // was `true` and now not provided
            elm.classList.remove(name);
        }
    }
    for (name in klass) {
        cur = klass[name];
        if (cur !== oldClass[name]) {
            elm.classList[cur ? "add" : "remove"](name);
        }
    }
}
export const classModule = { create: updateClass, update: updateClass };
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