前端的截图功能

依赖:html2canvas

function dataURLtoFile(dataurl, filename) {
  
        var arr = dataurl.split(','),
            mime = arr[0].match(/:(.*?);/)[1],
            bstr = atob(arr[1]), 
            n = bstr.length, 
            u8arr = new Uint8Array(n);
             
        while(n--){
            u8arr[n] = bstr.charCodeAt(n);
        }
         
        return new File([u8arr], filename, {type:mime});
    }
     
    //Usage example:
     
 
function takeScreenshot() {
    html2canvas(document.body,{
     allowTaint: true,
     foreignObjectRendering: true
    }).then(function(canvas) {
        //document.body.appendChild(canvas);
        var dataurl=canvas.toDataURL();
        var file = dataURLtoFile(dataurl,'cap.png');
        //var url = window.URL.createObjectURL(file);
        var a = document.createElement('a');
        var url = window.URL.createObjectURL(file);
        var filename = 'cap.png';
        a.href = url;
        a.download = filename;
        a.click();
        window.URL.revokeObjectURL(url);
        console.log(url);
         
    });
}