- 无界嵌入，在子应用window对象上绑定事件为什么不生效？
例如： 子应用中绑定 window.addEventListener('resize', fn);
同样在子应用中触发： window.dispatchEvent(new Event('resize'));
- 理解异步函数
function delay(ms, msg) { return new Promise((res, rej) => { setTimeout(() => res(msg), ms); }); } async function wait1(msg) { return delay(2000, msg); } async function wait2(msg) { const result = await delay(2000, msg); console.log('result = ', result); }
async function test() { let a = wait2('no'); console.log(a); let b = await wait1('ok'); console.log(b); return b; }
test(); // 先return Promise给外部，再执行函数体中的代码
- SVG响应式研究
data:text/html,
这段代码实现了自适应的正方形，与image的object-fit特性有什么不同？能否实现object-fit实现不了的特性？
自适应SVG矩形：
data:text/html,
/**
- EventTarget is a DOM interface implemented by objects that can receive events and may have listeners for them.
- MDN Reference
/
interface EventTarget {
/*
- Appends an event listener for events whose type attribute value is type. The callback argument sets the callback that will be invoked when the event is dispatched.
- The options argument sets listener-specific options. For compatibility this can be a boolean, in which case the method behaves exactly as if the value was specified as options's capture.
- When set to true, options's capture prevents callback from being invoked when the event's eventPhase attribute value is BUBBLING_PHASE. When false (or not present), callback will not be invoked when event's eventPhase attribute value is CAPTURING_PHASE. Either way, callback will be invoked if event's eventPhase attribute value is AT_TARGET.
- When set to true, options's passive indicates that the callback will not cancel the event by invoking preventDefault(). This is used to enable performance optimizations described in § 2.8 Observing event listeners.
- When set to true, options's once indicates that the callback will only be invoked once after which the event listener will be removed.
- If an AbortSignal is passed for options's signal, then the event listener will be removed when signal is aborted.
- The event listener is appended to target's event listener list and is not appended if it has the same type, callback, and capture.
- MDN Reference / addEventListener(type: string, callback: EventListenerOrEventListenerObject | null, options?: AddEventListenerOptions | boolean): void; /*
- Dispatches a synthetic event event to target and returns true if either event's cancelable attribute value is false or its preventDefault() method was not invoked, and false otherwise.
- MDN Reference / dispatchEvent(event: Event): boolean; /*
- Removes the event listener in target's event listener list with the same type, callback, and options.
- MDN Reference */ removeEventListener(type: string, callback: EventListenerOrEventListenerObject | null, options?: EventListenerOptions | boolean): void; }