javascript - 我想在画布渲染后收到警报

Question

我在带有文本的画布上绘制图像，但画布需要很长时间才能渲染。我想在画布渲染后收到警报。这是我的脚本：

function dz_res_click() {
  var canvas = document.getElementById("dz_residence_canvas");
  var context = canvas.getContext("2d");
  var residence = new Image();
  residence.src = "../../imgs/residence.jpg"
  var r_wlaya = document.getElementById("r_wlaya").value;
  residence.onload = function() {
    context.drawImage(residence, 0, 0, 2135, 2843);
    context.font = "bold 70px sans-serif";
    context.textAlign = "right";
    context.fillText(r_wlaya, 1596, 252);
  }
}

标签： javascriptjquery

Answer 1

这是解决方案。您只需添加警报。

residence.onload = function(){
    context.drawImage(residence, 0, 0, 2135, 2843);
    context.font = "bold 70px sans-serif";
    context.textAlign = "right";
    context.fillText(r_wlaya, 1596, 252);
    alert("javascript is synchronous, so unless there is a callback or promise, 
    functions execute in the order in which they are invoked.");
}