image exists 检查图像是否存在

形象存在检查图像是否存在。安装：npm install image-exists。用法：

var imageExists = require('image-exists');

var src = 'http://example.com/image.png';

imageExists(src, function(exists) {

  if (exists) {

    console.log(\"it's alive!\");

  } else {

    console.log(\"oh well\");

  }

});