<input type='file' class='upload-img' />

$('.upload-img').on('change',function(){
    var file = this.files[0];
        // 图片后缀  
        var suffix = file.name.split(".")[1];
        var reader = new FileReader();
        reader.readAsDataURL(file);
        reader.onload = function(e) {
            // base64编码
            image_base64 = this.result.split(",")[1];
            console.log(image_base64);
        }
    });