Detailed introduction to execution callbacks

You can easily add image content to canvas using a few simple commands built into the canvas API. It should be noted that you must wait until the image is fully loaded before you can operate it. The browser usually loads the image asynchronously while the page script is executing. If you try to render an image to the canvas before it is fully loaded, no image will be displayed. The following example will load an image of a tree bark texture as a tree trunk for use by the canvas. To ensure that the image is fully loaded before rendering , a callback method is provided here, that is, the subsequent code will only be executed when the image is loaded

1. HTML5-6 __Canvas: Insert a picture, and execute the callback when the picture is loaded

#Introduction: The following example will load a bark texture image as a trunk for canvas use. To ensure that the image is fully loaded before rendering, here A callback method is provided, that is, the subsequent code will only be executed when the image is loaded

2. Detailed explanation of the usage of the javascript some() function, javascriptsome_PHP tutorial

Introduction: Detailed explanation of the usage of javascript some() function, javascriptsome. Detailed explanation of the usage of javascript some() function, javascriptsome parameter description callback: The callback function to be executed for each array element. thisObject: The this pair defined when executing the callback function

3. javascript some() function usage details, javascriptsome

Introduction: Detailed explanation of the usage of javascript some() function, javascriptsome. Detailed explanation of the usage of javascript some() function, javascriptsome parameter description callback: The callback function to be executed for each array element. thisObject: This pair defined when executing the callback function

4. javascript - How does AJAX achieve asynchronous implementation?

Introduction: I have seen the source code of the AJAX method, which is to call a callback in the AJAX method, first execute the AJAX method and then execute the callback. What is the difference between this and the ordinary reference function? What's the difference? So where is the experience of AJAX asynchronous callback;

5. php jquery written in dwt does not execute callback, but html can execute callback, please give me some advice.

Introduction: The following js code is written in the template file dwt. Why is there no callback? If written in html, the callback can be called``` function getVal() { $.getJSON(" bus_sel.php", { sf_id : $("#sf_id").val() }, function(json) { alert(1111); var ds_id = $("#ds_id"); $.each(json, function( index, array) { alert(&q

6. $.getJSON usage instructions in JQuery_jquery

Introduction: getJSON is commonly used in jQuery to call and obtain the remote JSON string, convert it into a JSON object, and execute the callback function if successful.

#7. jquery. $getjson calls and gets the remote JSON string problem_javascript skills

Introduction: getJSON is commonly used in jQuery to call and get the remote JSON string and convert it to JSON Object, if successful, the callback function will be executed. This article will introduce it in detail. Friends who need it can refer to

8. Extjs4 message box removes the close button (similar to Ext.Msg. alert)_extjs

Introduction: Similar to Ext.Msg.alert(); but there is no close button. Due to the close button in the Extjs4 message box, the callback function is not executed. Click to close. After pressing the button, close the window directly. Next, I will introduce in detail how to remove the close button

9. How to dynamically insert JS and immediately execute the callback function_javascript skills

Introduction: This article mainly introduces the method of dynamically inserting JS and immediately executing the callback function. The example analyzes the related techniques of dynamically inserting the JS file and executing the callback function. Friends in need can refer to the following

[Related Q&A recommendations]:

javascript - wx.getLocation cannot execute the callback correctly, probably because of the scope

javascript - $.post() in the loop starts executing the callback function only after the loop ends

javascript - How to load js files on demand?

Front-end - Please use javascript in this case whether you need to manually release the object

javascript - angularjs ocLazyLoad loading callback issue

The above is the detailed content of Detailed introduction to execution callbacks. For more information, please follow other related articles on the PHP Chinese website!