useful tools

[yanlee26]

throttle

            let stattime = 0;
            return function (...args) {
                let curTime = new Date();
                if (curTime - stattime >= delay) {
                    fn.apply(this, args);
                    stattime = curTime;
                }
            }
        }

debounce

            let timer;
            return function (...args) {
                let that = this;
                clearTimeout(timer);
                timer = setTimeout(fn.bind(that, ...args), time);
            }
        }

simple promise

class Promise {
 constructor(fn) {
   this.status = 'Pending'
   setTimeout(() => {
     fn((data) => {
       this.resolve(data)
     }, (error) => {
       this.reject(error)
     })
   })
 }
 
 resolve(data) {
   if (this.status === 'Pending') {
     this.success(data)
     this.status = 'Fulfilled'
   }
 }

 reject(error) {
   if (this.status === 'Pending') {
     this.error(error)
     this.status = 'Rejected'
   }
 }

 then(success, error) {
   this.success = success
   this.error = error
 }
}

let p1 = new Promise((resolve, reject) => {
 // reject('hello error');
 setTimeout(() => {
   resolve('hello promise')
 }, 1000)
})

p1.then((data) => console.log(data), (err) => console.log(err))

cancel promise

const p1 = new Promise((resolve, reject) => {
  setTimeout(() => { // 异步操作
      resolve('start')
  }, 1000);
});

p1.then(result=> {
   console.log('a', result); 
   return Promise.reject('中断后续调用'); 
// 此时rejected的状态将直接跳到catch里，剩下的调用不会再继续
}).then(result => {
   console.log('b', result);
}).then(result => {
   console.log('c', result);
}).catch(err => {
   console.log(err);
});

// a start
// 中断后续调用

array flatten

let arr = [[1, 2], 3, [[[4], 5]]]; // 数组展平
function flatten(arr) {
    return [].concat(
        ...arr.map(x => Array.isArray(x) ? flatten(x) : x)
    )
}

getElementsByClassName

  function getByClass(cName) {
      if ('getElementsByClassName' in this) {
          return this.getElementsByClassName(cName);
      }
      cName = cName.replace(/(^\s+|\s+$)/g, '').split(/\s+/g);
      let eles = this.getElementsByTagName('*');
     for (let i = 0; i < cName.length; i++) {
        let reg = new RegExp(`(^| )${cName[i]}( |$)`);
        let temp = [];
        for (let j = 0; j < eles.length; j++) {
            let cur = eles[j];
            let {className} = cur;
            if (reg.test(className)) {
                temp.push(cur);
            }
        }
        eles = temp;
     }
     return eles;
  }
  console.log(content.getByClass('c1 c2 '));