npm 报错：
These dependencies were not found:
* canvas in ./node_modules/pdfh5/js/pdf.js
* dommatrix/dist/dommatrix.js in ./node_modules/pdfh5/js/pdf.js
* web-streams-polyfill/dist/ponyfill.js in ./node_modules/pdfh5/js/pdf.worker.js
To install them, you can run: npm install --save canvas dommatrix/dist/dommatrix.js web-streams-polyfill/dist/ponyfill.js
不能直接执行他给的命令，那样会报新的错误
第一步先执行：
npm install canvas@2.8.0 --ignore-scripts只执行npm install canvas会报新的错误
第二步执行：
npm install --save dommatrix第三步执行：
npm install --save web-streams-polyfill然后就可以运行成功啦
我的node和npm版本如下:
