don t know js

(){Console. log (new Date ()-startTime );}, 100)What is the last print? The correct answer is that it depends on the amount of time it takes for the JS to be synchronized later.That is, MAX (synchronous execution time, 100). If so, you have to check the setTimeout running mechanism.2. setTimeout running mechanismThe running mechanism of setTimeout and setInterval is to remove the specified code from this execution. When the next Event Loop is execute

it may conflict with regular expression literals. The array of JS can be accessed by a numeric subscript in the form of a string, because the elements of the array are actually properties of the array object. Delete can be used to remove elements from an array, but because an element is an attribute, delete leaves a "hole" in the array; using the splice method may be a better approach. For example, to delete the 3rd element of the ARR array, you c

JavaScript closures are the knowledge that JS development engineers must gain in-depth understanding. In March, I wrote a blog, "JavaScript closures," the blog is simply a description of the closure of the work process and a few examples, and did not go into the inquisitive, to understand it!now, with a more in-depth understanding of JavaScript, and just finished reading the book, " You Don't know the JavaS

with the simplest API available and makes the smallest assumptions. You can use it for different types of tests, analysis,Even provide executable code examples. It is out of the box and generates a CI-friendly output that is usually as simple as running ' go test '. Of course, it also supports advanced features such as running tests in parallel, tag skipping, and so on. # # Race condition detection You may already know goroutines, which is used in Go

What is the scope? A: In the JavaScript you don't know, the scope is a set of rules for finding variables by name. Old saying there is "no rules inadequate surrounding area", but no radius, rules and who to use? So the individual understanding scope is "rule" + "radius". Scopes are determined at the time of creation. Who has scope? Answer: Global, function. Why do we have scopes? A: As already mentioned, the scope is "

In the previous article, we defined scopes as "a set of rules for managing and maintaining variables," and then it's time to discuss the scope of JS in depth, first of all we need to know that there are two main types of work in scope, one is lexical scope, one is dynamic scope, JavaScript uses lexical scopes, and interested in dynamic scopes can be self-google. 1. Lexical phase First of all, we have to und

comma, and the value cannot be a function/undefined/nan Can be added with a comma, can be any value JSON to JS object------json.parse (str)JS object to JSON------json.stringify (obj)Prior to this project development only contacted and used the Json.parse () and the Json.stringify () method of the first parameter, and then did not go to the drill, in an accidental opportunity to see the othe

bit moreRecognize the floating point arithmetic of javascriptThe students who have studied JS know that the numbers in JS are represented by floating-point number, and the double-precision floating-point numbers are indicated using IEEE 754 standard. 　IEEE 754 Standard floating-point number Introduction (Oh, this is the University of the composition of the reas

-screen scenarios, allowing this 4.0 to start with a new faeture glow. This also means that you can drag a split-screen control to another sub-screen in one app, or even a separate screen between applications. Maybe it can be used to drag and drop pictures quickly, or. Whatever you want to do.Of course, from a development dog's point of view, there is a bit of a security risk: If you pass the data through a drag-and-drop, you don't even know what the

The JavaScript array you don't knowBelieve that every JavaScript learner, will be to understand the various basic JS data types, arrays is a combination of data, this is a very basic and very simple concept, his content is not much, learn it is not a difficult thing. But this article is important to introduce is not the usual Array we see, but ArrayBuffer.I write a lot of things because to complete some specific functions and deliberately summed up, c

Is the weak type good? Fortunately, I don't know what I need because I started php. it makes me more and more confused. nbsp; the code is full of ifemptyifempty nbsp; if (! Empty ($ CFG- gt; aaaa) {} nbsp; nbsp; search for $ CFG- gt; aaaa never showed up, vomit blood on the spot, then, the system does not vomit after a few more times. nbsp; nbsp weak type? Fortunately, I don't know I started to use php

You want to use the PATH_INFO function. But I don't know where to add it? This is a functional Web site for viewing the source code of the web page. this is www. vipcha. net5. what I want to achieve is to add a Web site based on www.vipcha.net5www.baidu.com. The code is as follows. Thank you for PHPcode lt ;? Php $ huyuan; @ requi want to use the PATH_INFO function. But I don't know where to add it? This i

Puzzle One:First look at the example:function test () {message = "HI";} Test (); alert (message);Will output the string "HI"Variables defined using var inside a function are local variables, and variables that omit the var operator are global variables.Puzzle Two:alert (undefined = = null)The result is "true"We know that in JS there are basic types and reference types, and the base type contains number, Str

Whether you believe it or not, CSS and JavaScript begin to overlap, just as CSS adds more functionality. When I wrote the article "5 ways that you might not know about CSS and JavaScript interacting with each other", people were amazed at how JavaScript and CSS overlapped. Today, I'll focus on 7 kinds of work that you can do with CSS-no javascript or pictures. 　　 [email protected]When using features that some browsers might not have, every good front-

S: The For loop here refers to the language of JS oh ... The composition structure of the For loop; The code is as follows Copy Code Why should var i;//be defined in this? See jquery sourceFor (i=0 iThis is the loop block.} This is a very ordinary "woman", but do you really know her? The following fields are divided: Red: Defining blocksGreen: Judgment blockBlue: C

I am crazy about the error of forms. The problem is: The form is submitted directly using the submit button area. it is no problem (the method is to think of a form to different page actions) however, if a problem occurs when you press the button to implement the submission using JS, you can go to the page. However, the result is that the database does not respond, and you cannot modify the insert operation! However, I don't

"successful" and call resolve to change the state of promise . Otherwise we think it is "failed", call reject and pass a number of parameters. As a cause of failure.Runs GetNumber and then passes two parameters, then the then method can accept two parameters. callback for the first corresponding resolve. A callback for the second corresponding reject .So we were able to get the data they sent. Run this code multiple times. You will randomly get the following two results:OrHow to use 2.4 catchWe

. Understand or become familiar with C, C + +,. NET 13. Familiar with JDK configuration, environment variable 14. Database Oracle must learn, others better understand more than one (Mysql,sql server,access==) o Racle: Views, indexes, stored procedures, triggers, cursors, packages, common functions = = 15. Principles of database principle, lock mechanism, table connection, complex query statement (working experience), performance tuning, lock table and solution = = 16.JDBC, connection pool 17.Aja

let declares are valid only in blocks of code (usually the block of code formed by {}).2. Variable elevation vs temporary Dead ZoneAs we all know, the variables declared by VAR will have the function of variable promotion, as followsConsole.log (a); // 1 var a=1; Console.log (b); // undefined var b;As can be seen, although the code in the console call a before, declare a after, but because in JS, the fu

You want to use the PATH_INFO function. But I don't know where to add it? This is a functional website for viewing Web page source code. The code is as follows. Thank you for using the PATH_INFO function. But I don't know where to add it? This is a function for viewing Web page source code. The URL is like this. Www.vipcha.net/5/ The function I want to implement is as follows: Www.vipcha.net/5/www.baidu.com