js根据图片地址转DataURL和DataURL转Blob 1.根据图片URL直接获取到DataUrlfunction convertImgToDataURLviaCanvas(url, callback, outputFormat){ var img = new Image(); img.crossOrigin = 'Anonymous'; img.onload = function(){ var canvas = document.createElement('CANVAS'); var ctx = canvas.getContext('2d'); var dataURL; canvas.height = this.height; canvas.width = this.width; ctx.drawImage(this, 0, 0); dataURL = canvas.toDataURL(outputFormat); callback(dataURL); canvas = null; }; img.src = url; }function convertFileToDataURLviaFileReader(url, callback){ var xhr = new XMLHttpRequest(); xhr.responseType = 'blob'; xhr.onload = function() { var reader = new FileReader(); reader.onloadend = function () { callback(reader.result); } reader.readAsDataURL(xhr.response); }; xhr.open('GET', url); xhr.send(); }2.DataURL转Blobfunction dataURLtoBlob(dataurl) { 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 Blob([u8arr], {type:mime}); }

js获取字符串中包含的最后一个字母所在序号 function getLastLetterPosition(str) { let _pos = 0; for (let i = 0; i < str.length; i++) { if (new RegExp("^[a-zA-Z]$").test(str[i])) { _pos = i; } } console.log('Last letter position:', _pos); return _pos; }