function enter()

in assets/js/vue.js [8116:8265]
77 lines of code
32 McCabe index (conditional complexity)

  function enter (vnode, toggleDisplay) {
    var el = vnode.elm;

    // call leave callback now
    if (isDef(el._leaveCb)) {
      el._leaveCb.cancelled = true;
      el._leaveCb();
    }

    var data = resolveTransition(vnode.data.transition);
    if (isUndef(data)) {
      return
    }

    /* istanbul ignore if */
    if (isDef(el._enterCb) || el.nodeType !== 1) {
      return
    }

    var css = data.css;
    var type = data.type;
    var enterClass = data.enterClass;
    var enterToClass = data.enterToClass;
    var enterActiveClass = data.enterActiveClass;
    var appearClass = data.appearClass;
    var appearToClass = data.appearToClass;
    var appearActiveClass = data.appearActiveClass;
    var beforeEnter = data.beforeEnter;
    var enter = data.enter;
    var afterEnter = data.afterEnter;
    var enterCancelled = data.enterCancelled;
    var beforeAppear = data.beforeAppear;
    var appear = data.appear;
    var afterAppear = data.afterAppear;
    var appearCancelled = data.appearCancelled;
    var duration = data.duration;

    // activeInstance will always be the <transition> component managing this
    // transition. One edge case to check is when the <transition> is placed
    // as the root node of a child component. In that case we need to check
    // <transition>'s parent for appear check.
    var context = activeInstance;
    var transitionNode = activeInstance.$vnode;
    while (transitionNode && transitionNode.parent) {
      context = transitionNode.context;
      transitionNode = transitionNode.parent;
    }

    var isAppear = !context._isMounted || !vnode.isRootInsert;

    if (isAppear && !appear && appear !== '') {
      return
    }

    var startClass = isAppear && appearClass
      ? appearClass
      : enterClass;
    var activeClass = isAppear && appearActiveClass
      ? appearActiveClass
      : enterActiveClass;
    var toClass = isAppear && appearToClass
      ? appearToClass
      : enterToClass;

    var beforeEnterHook = isAppear
      ? (beforeAppear || beforeEnter)
      : beforeEnter;
    var enterHook = isAppear
      ? (typeof appear === 'function' ? appear : enter)
      : enter;
    var afterEnterHook = isAppear
      ? (afterAppear || afterEnter)
      : afterEnter;
    var enterCancelledHook = isAppear
      ? (appearCancelled || enterCancelled)
      : enterCancelled;

    var explicitEnterDuration = toNumber(
      isObject(duration)
        ? duration.enter
        : duration
    );

    if (explicitEnterDuration != null) {
      checkDuration(explicitEnterDuration, 'enter', vnode);
    }

    var expectsCSS = css !== false && !isIE9;
    var userWantsControl = getHookArgumentsLength(enterHook);

    var cb = el._enterCb = once(function () {
      if (expectsCSS) {
        removeTransitionClass(el, toClass);
        removeTransitionClass(el, activeClass);
      }
      if (cb.cancelled) {
        if (expectsCSS) {
          removeTransitionClass(el, startClass);
        }
        enterCancelledHook && enterCancelledHook(el);
      } else {
        afterEnterHook && afterEnterHook(el);
      }
      el._enterCb = null;
    });

    if (!vnode.data.show) {
      // remove pending leave element on enter by injecting an insert hook
      mergeVNodeHook(vnode, 'insert', function () {
        var parent = el.parentNode;
        var pendingNode = parent && parent._pending && parent._pending[vnode.key];
        if (pendingNode &&
          pendingNode.tag === vnode.tag &&
          pendingNode.elm._leaveCb
        ) {
          pendingNode.elm._leaveCb();
        }
        enterHook && enterHook(el, cb);
      });
    }

    // start enter transition
    beforeEnterHook && beforeEnterHook(el);
    if (expectsCSS) {
      addTransitionClass(el, startClass);
      addTransitionClass(el, activeClass);
      nextFrame(function () {
        removeTransitionClass(el, startClass);
        if (!cb.cancelled) {
          addTransitionClass(el, toClass);
          if (!userWantsControl) {
            if (isValidDuration(explicitEnterDuration)) {
              setTimeout(cb, explicitEnterDuration);
            } else {
              whenTransitionEnds(el, type, cb);
            }
          }
        }
      });
    }

    if (vnode.data.show) {
      toggleDisplay && toggleDisplay();
      enterHook && enterHook(el, cb);
    }

    if (!expectsCSS && !userWantsControl) {
      cb();
    }
  }