How to determine a browser or node environment?
node in the window is undefined; setImmediate is defined, is not defined in the browser
timer stage: This stage will perform setTimeout and setInterval
check stages: execution setImmediate
macro task [task] macro task: script (code pages), setTimeout, setInterval, I / O events, UI interaction event (click event)
micro task [job] 微任务： Promise、process.nextTick、Promise().then()
Macro task can have multiple queues
Only a micro-task queue
SetTimeout between tasks, the smaller the number of milliseconds of delays in the implementation, inside the front row of the queue
In node inside, timers (setTimeout, setInterval) will give priority to setImmediate
setTimeout(() => {
console.log('setTimeout')
}, 0); // time of greater than 1000, will first perform setImmediate
setImmediate（（）=> { console.log('setImmediate')}）
console.log('start');
setTimeout(function (){
console.log('timeout');
},10);
new Promise((resolve) => {
console.log('promise');
resolve()
setTimeout(() => {
console.log ( 'Promsie in setTimeout');
},0);
}).then(() => {
console.log('then');
});
console.log('end');
Operating mechanism
1. Perform a macro task execution stack.
2. encountered in implementation of micro tasks, to add to the micro-micro-task job queue.
3. The current macro task is finished, the micro-mission tasks in the queue immediately.
4. The current task execution queue micro task is completed, check the rendering, GUI thread to take over the rendering.
5. When rendering is complete, js thread to take over, once the next event loop open, once the macro task (event queue to take) under execution.