I have been using below script to upload images which happens to works fine. Hope this will help you too.

#HTML #JS

jQuery('document').ready(function(){
    
        var input = document.getElementById("file");
        var formdata = false;
        if (window.FormData) {
            formdata = new FormData();
        }
        input.addEventListener("change", function (evt) {
        
            var i = 0, len = this.files.length, img, reader, file;
    
            for ( ; i < len; i++ ) {
                file = this.files[i];
    
                if (!!file.type.match(/image.*/)) {
                    if ( window.FileReader ) {
                        reader = new FileReader();
                        reader.onloadend = function (e) { 
                            //showUploadedItem(e.target.result, file.fileName);
                        };
                        reader.readAsDataURL(file);
                    }
                
                    if (formdata) {
                        formdata.append("image", file);
                        formdata.append("extra",'extra-data');
                    }
                
                    if (formdata) {
                        jQuery('div#response').html('<br /><img src="ajax-loader.gif"/>');
                    
                     
                        jQuery.ajax({
                            url: "upload.php",
                            type: "POST",
                            data: formdata,
                            processData: false,
                            contentType: false,
                            success: function (res) {
                             jQuery('div#response').html("Successfully uploaded");
                            }
                        });
                    }
                }
                else
                {
                    alert('Not a vaild image!');
                }   
            }
    
        }, false);
 
    });

Here you are not using a plugin and stuff. You can change the code as you want. You are not blindly coding here. This is the core functionality of any jQuery file upload. Actually Javascript.

Hope this helps.

I have been using the below script to upload images which happens to work fine.

#HTML 

#JavaScript

jQuery('document').ready(function(){
    var input = document.getElementById("file");
    var formdata = false;
    if (window.FormData) {
        formdata = new FormData();
    }
    input.addEventListener("change", function (evt) {
        var i = 0, len = this.files.length, img, reader, file;

        for ( ; i < len; i++ ) {
            file = this.files[i];

            if (!!file.type.match(/image.*/)) {
                if ( window.FileReader ) {
                    reader = new FileReader();
                    reader.onloadend = function (e) {
                        //showUploadedItem(e.target.result, file.fileName);
                    };
                    reader.readAsDataURL(file);
                }

                if (formdata) {
                    formdata.append("image", file);
                    formdata.append("extra",'extra-data');
                }

                if (formdata) {
                    jQuery('div#response').html('<br /><img src="ajax-loader.gif"/>');

                    jQuery.ajax({
                        url: "upload.php",
                        type: "POST",
                        data: formdata,
                        processData: false,
                        contentType: false,
                        success: function (res) {
                         jQuery('div#response').html("Successfully uploaded");
                        }
                    });
                }
            }
            else
            {
                alert('Not a vaild image!');
            }
        }

    }, false);
});

Here you are not using a plugin and stuff. You can change the code as you want. You are not blindly coding here. This is the core functionality of any jQuery file upload. Actually Javascript.