js读取txt文件

在此记录一下优化历程，从复杂到简洁，从慢到快

FileReader

网上搜到的方法大多数使用FileReader来实现

     const file = '../test.txt'
         const reader = new FileReader()
         reader.readAsText(file, "UTF-8")
         let dataArr = []
         reader.onload = (evt) => {
    
    
           const fileString = evt.target.result
           const count = fileString.trim().split('\n').length
           for (let index = 1; index < count; index++) {
    
    
             const fileline = fileString.split("\r\n")[index].split(",")[0]
             const filelineNumber = (fileline.split(/\s+/)).map(Number)
             dataArr.push(filelineNumber)
           }
         }

ajax+FileReader

感觉和上面那个没有本质的区别，都很慢

  urlToBlob(file_url) {
    
    
      return new Promise(function (resolve, reject){
    
    
             let xhr = new XMLHttpRequest();
              xhr.open("get", file_url, true);
              xhr.responseType = "blob";
              xhr.onload = function () {
    
    
                if (this.status == 200) {
    
    
                  const reader = new FileReader()
                  reader.onload = function () {
    
    
                    resolve(reader.result)
                  }
                  reader.readAsText(this.response);
                }else{
    
    
                  console.log('err');
                }
              };
              xhr.send();
      })
    },

       this.urlToBlob('/static/test.txt').then(res => {
    
    
         const fileString = res
         // console.log('原始test文件',res);
         const count = fileString.trim().split('\n').length
         for (let index = 1; index < count; index++) {
    
    
           const fileline = fileString.split("\r\n")[index].split(",")[0]
           const lineValue = fileString.split("\r\n")[index].split(",")[1]
         }
      })

fetch

实测这里是最快的，而且最简洁，我有15w条数据，几乎瞬间处理完

      //说明还没有存储过，需要先请求，后存储，再返回 
      let resMesh = await fetch(txtUrl).then(res => res.text())
      
      // 处理点文件
      let pointRows = resMesh.split("\n");
      for (let i = 1; i < pointRows.length-1; i++) {
    
    
          let point = pointRows[i];
          let p = point.split(" ");//这里是分割每一行数据，逗号就写逗号，空格就空格
          //这里已经处理好了，p[0],p[1],p[2]...就是我们获取到的每一行数据
      }