+= 赋值运算符

  1. <!DOCTYPE html>
  2. <html>
  3. <body>
  4.  
  5. <h1>+= 运算符</h1>
  6.  
  7. <p id="demo"></p>
  8.  
  9. <script>
  10. var x = 7;
  11. x += 8;
  12. document.getElementById("demo").innerHTML = x;
  13. </script>
  14.  
  15. </body>
  16. </html>