一种字符串拼接的高效方法 ​

// prepare a long array
const arr = [];
for (let i = 0; i < 10000; i++) {
  arr.push("item" + i);
}

function testByForLoop1() {
  const tsStart = +new Date().valueOf();
  let html = "<ul>";
  for (let i = 0, len = arr.length; i < len; i++) {
    html += `<li>${arr[i]}</li>`;
  }
  html += "</ul>";
  console.log("testByForLoop1: " + (+new Date().valueOf() - tsStart));
}

function testByForLoop2() {
  const tsStart = +new Date().valueOf();
  let html = "<ul>";
  for (let i = 0, len = arr.length; i < len; i++) {
    html += "<li>" + arr[i] + "</li>";
  }
  html += "</ul>";
  console.log("testByForLoop2: " + (+new Date().valueOf() - tsStart));
}

function testByArrayJoinMethod() {
  const tsStart = +new Date().valueOf();
  let html = "<ul><li>";
  html += arr.join("</li><li>");
  html += "</li></ul>";
  console.log("testByArrayJoinMethod: " + (+new Date().valueOf() - tsStart));
}

testByForLoop1();
testByForLoop2();
testByArrayJoinMethod();