javascript closure interview question

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Closures and scope chain is a more important concept in JavaScript, these two days to read some information, the relevant knowledge points to the following summary. JavaScript takes the lexical scope (lexical scoping), where the function execution depends on the variable scoped by the function definition, not when the function is executed. As an example of the following code fragment, generally (based on t

example: var o = (function () { var a = 1 var b = 42 return { foo: function () { console.log(a + b) return b } }})()I also want to shake my mind: _ proto _ in IE9 is invalid. Therefore, the getter method added to Object. prototype is still valid in IE9. If your engine is well implemented, you cannot. You can try to prove it with Hall logic ...... However, if the engine does not support _ proto _ (it seems that IE has not supported it for a long time), you can inject Object

(); Counter_1.getcounter (); //0counter_2.getcounter (); //0counter_1.setcounter (88); Counter_2.getcounter (); //04. Fourth Example: impersonation of block-level scopesin Java ,C and Many other programming languages have the concept of block-level scope, in Java as an example:for (int i = 0; i There is no block-scoped concept in JavaScript, such as:for (var i = 0; iIn many cases, in order to not pollute the global namespace, you can use closures t

Nanda's articles have benefited me a lot. Learn JavaScript closures (Closure)Problem:In the words of doing task2 little exercise 4 round the picture encountered a problem. The original is to press which button to play to the corresponding picture. But actually the last value comes out at 5.For example, here is a simplified example. for (var i=1;i) { E[i].onclick=function() { console.log (i); };

at the closure problem. I set four buttons and click on each button to return the name of the response. Click to run, but the result is all btn5; We sat down with the analysis just now, first to invoke the anonymous function-> find I, not find->btninit (), find I in the For loop. Found it. We know that only the end of the function call is released, and I in the for is always visible, so the last I value is preserved. So how to solve it

the lower version of IE. Example 3: for (var i = 0; i This principle is similar to the above. Millet front-end closure interview questions: function repeat (func, times, wait) { }//It can return a new function, such as using var repeatedfun = repeat (alert, 5000) //Calling This repeatedfun ("Hellworld") //Will alert 10 times HelloWorld, each interval 5 seconds My answer:

Opening Speech: For friends with existing work experience, it may not be very important to interview questions, but if you apply for an ordinary programmer, I believe that many companies will still come up with a set of interview questions, which may not affect the entire interview, but it will undoubtedly win the first impression to do a good

A netizen asked a question, such as the next HTML, why each output is 5, instead of clicking each p, alert out the corresponding 1,2,3,4,5. There are several ways to solve this problem 1. Save the variable i on each paragraph object (p) function init () { var pary = document.getElementsByTagName ("P"); for (var i=0; i 2. Save the variable i to the anonymous function itself function Init2 () { var pary =

A netizen asked a question, such as the next HTML, why click All the paragraph p output is 5, instead of alert out corresponding 0,1,2,3,4. The above scenes are often encountered by beginners. Gets the collection of HTML elements to iterate over the element add event. Gets the corresponding index (event handler) in the incident response function. But each fetch is the index of the last loop. The

JavaScript. explain the principle of prototype inheritance?AMD vs CommonJS?AMD vs CMD?extended JavaScript built-in objects?how to get query string parameters from the URL of the browser?what is "use strict" and what are the advantages and disadvantages of using it?A. common compatibility issues?What are the new features and elements removed from HTML5? How do I handle browser compatibility issues with HTML

Array de-weight is a frequently asked question in the interview[HTML]View PlainCopy var arr=[1,3,4,52,4,5,4,8,7,6]; The first method: Use the indexof in ES5 to remove the weight:[JavaScript]View PlainCopy function arr1 () { var n=[]; For (var i=0;i if (N.indexof (Arr[i]) ==-1) { N.push (Arr[i]); } } return n; }//Define an emp

A netizen asked a question, as shown in the following HTML, why is the output of all P paragraphs 5 rather than alert corresponding to 0, 1, 2, 3, and 4. The above scenarios are common for beginners. That is, you can obtain the HTML Element Set and add events to the element cyclically. Obtain the corresponding index in the Event Response Function (event handler. However, each query is the index of the last loop. The reason is that beginners do

A netizen asked a question, as shown in the following html, why is the output of all p paragraphs 5 rather than alert corresponding to 0, 1, 2, 3, and 4. The above scenarios are common for beginners. That is, you can obtain the HTML Element Set and add events to the element cyclically. Obtain the corresponding index in the event Response Function (event handler. However, each query is the index of t

scope and closure of the necessary, JS implementation of some of the underlying concepts and theoretical knowledge. Recurrence of the classic case list 1, the classic case of a Copy Code code as follows: /* A piece of code under the Global (window) field * * function A (i) { var i; alert (i); }; A (10); Question: What does the above code output? Answer: Yes, just pop 10

the generator is essentially the keyword of yield in the function.The difference between yield and return is that the function encounters yield and does not end, just hang, but return is over.Yield has a send () method, which can be assigned a value of yieldFive, write a Fibonacci algorithm:def fib (n): = 0, 1 while a N: Print(A, end=") = B, A + b Print (a) fib (1000)Six,Greedy match and non-greedy match, the former match as long as possible, the latter match as

internal function doadd is a closure that gets the value of the incoming parameter num1,num2 and global variable inum, Doadd does not accept arguments, add the last step calls Doadd, and returns two arguments and global variables. You can see that the values used by Doadd are obtained in the execution environment. Here are a few examples on the web to understand lexical scopes and closures Copy Code code as follows: , Case a /* A

Original reference: http://blog.csdn.net/gaoshanwudi/article/details/7355794Beginners often encounter, that is, get the HTML element collection, loop to add events to the element. The corresponding index is obtained in the event response function (handler). But each fetch is the index of the last loop. The reason is that beginners do not understand the characteristics of JavaScript closures.A netizen asked a quest