HttpQueue.js

export default class HttpQueue {
  
  constructor (queryFunction) {
    this.requesting = false
    this.stack = []
    this.queryFunction = queryFunction
  }
  
  add (options, resolve, reject) {
    if (this.stack.length < 2) {
      return new Promise ((resolve, reject) => {
        this.stack.push({
          options,
          resolve,
          reject
        })
        this.makeQuery()
      })
    }
    return new Promise ((resolve, reject) => {
      this.stack[1] = {
        options,
        resolve,
        reject
      }
      this.makeQuery()
    })
    
  }
  
  makeQuery () {
    if (! this.stack.length || this.requesting) {
      return null
    }
    
    this.requesting = true
    
    this.queryFunction(this.stack[0].options).then(response => {
      this.stack[0].resolve(response)
      this.requesting = false
      this.stack.splice(0, 1)
      this.makeQuery()
    }).catch(error => {
      this.stack[0].reject(error)
      this.requesting = false
      this.stack.splice(0, 1)
      this.makeQuery()
    })
  }
}