hoisting

JavaScript hoisting function vs function variable

由 杀马特。学长 韩版系。学妹 提交于 2019-12-02 02:45:38
Here is my javascript code : console.log(a); c(); b(); var a = 'Hello World'; var b = function(){ console.log("B is called"); } function c(){ console.log("C is called"); } Now here is output : undefined hoisting.html:12 C is called hoisting.html:6 Uncaught TypeError: b is not a function My question is regarding why c() and b() behaving differently. And b should throw error something like b is not defined. soundyogi A Function Declaration will be hoisted along with its body. A Function Expression not, only the var statement will be hoisted. This is how your code "looks" like to the interpreter

Hoisting and variable scope

由 一世执手 提交于 2019-12-02 01:28:29
问题 Would someone help explain why the two snippets of code below print out different results? The difference is inside the conditional statement. In the first, there is a local variable assignment of 'Jack' to name, and the conditional is truthy (meaning !name evaluates to true). In the second, the same name 'Jack' is assigned but to the global variable name, but the conditional is falsy (!name is false). My question is, if all else is the same, why would the first conditional be true and the

Variable not hoisted

由 自作多情 提交于 2019-12-01 23:05:11
问题 In Javascript variables are hoisted to the top of the scope they are declared within. However in the following code it seems that the variable myvar is not hoisted. <html> <body> </body> </html> <script type="text/javascript"> console.log(typeof myvar); var myvar = "value"; console.log(typeof myvar); </script> The output of the above is: undefined string I expected that the first line would say "string" because myvar is supposed to be hoisted to above it. Why isn't this so? 回答1: Variable

Confused about hoisting

由 こ雲淡風輕ζ 提交于 2019-12-01 22:34:54
consider these slightly two different versions of hoisting... mylocation = "dublin" function outputPosition() { alert(mylocation); mylocation = "fingal" ; alert(mylocation); } outputPosition(); This will output "fingal" and then "fingal" mylocation = "dublin" function outputPosition() { alert(mylocation); var mylocation = "fingal" ; alert(mylocation); } outputPosition(); This will output "undefined" and "fingal" Why? Once you declare variable using var keyword within a javascript function and no matter where you put this declaration - at the top of the function or at the buttom, it will be

Hoisting and variable scope

由 痴心易碎 提交于 2019-12-01 20:53:07
Would someone help explain why the two snippets of code below print out different results? The difference is inside the conditional statement. In the first, there is a local variable assignment of 'Jack' to name, and the conditional is truthy (meaning !name evaluates to true). In the second, the same name 'Jack' is assigned but to the global variable name, but the conditional is falsy (!name is false). My question is, if all else is the same, why would the first conditional be true and the second is false if what is changed is inside the conditional body? My only explanation is that the body

Function names defined as parameters to a function call aren't hoisted. Why not?

由 无人久伴 提交于 2019-12-01 20:08:34
Consider the following code. <!DOCTYPE html> <script> console.log(a); function a() {} </script> Notice that a is seemingly accessed before it is defined. The console output is: ( jsfiddle ) function a() {} Function and variable names are defined before any other code runs, so the console.log call works here. This is called hoisting . But this doesn't work if the function is defined as a parameters in a function call. Look at this code. <!DOCTYPE html> <script> function a() {} a(function b() {}); console.log(b); </script> Notice that the function b is defined inside of a call to a . Not inside

Javascript variable and function hoisting

由 女生的网名这么多〃 提交于 2019-12-01 10:57:46
david sharif made a JS quiz which pretty much looks like- var foo=1; function bar(){ return foo; foo=10; function foo(){} var foo =5; } typeof bar();//? In my understanding, functions are hosited first and then variable declared inside. the hosited form of the function would be something like (correct me if i am wrong)- var foo=1; function bar(){ function foo(){} var foo; return foo; foo=10; foo =5; } typeof bar();//? why typeof bar() is function not undefined? Is this because of, at the time of function execution, it finds the first foo (which is a function) and returns happily without

which and how javascript function will be called if we have 2 function declarations with the same name?

由 余生颓废 提交于 2019-12-01 08:40:29
Take a test: <script> function say() { alert( "ABOVE" ); } say(); function say() { alert( "BELOW" ); } </script> The result is "BELOW" for all test (Chrome, Firefox, IE). How does javascript interpreter work in this case? http://jsfiddle.net/jcv6l/ << run the code. Basically, because of hoisting, which pulls all function declarations to the top of the current scope, the interpreter is basically doing this: function say() { alert( "ABOVE" ); } function say() { alert( "BELOW" ); } say(); That is why it always ends up alerting below KernelPanik In this case the interpreter parses the function

which and how javascript function will be called if we have 2 function declarations with the same name?

由 岁酱吖の 提交于 2019-12-01 06:28:31
问题 Take a test: <script> function say() { alert( "ABOVE" ); } say(); function say() { alert( "BELOW" ); } </script> The result is "BELOW" for all test (Chrome, Firefox, IE). How does javascript interpreter work in this case? http://jsfiddle.net/jcv6l/ << run the code. 回答1: Basically, because of hoisting, which pulls all function declarations to the top of the current scope, the interpreter is basically doing this: function say() { alert( "ABOVE" ); } function say() { alert( "BELOW" ); } say();

Make sure a Javascript script is first to run?

由 自闭症网瘾萝莉.ら 提交于 2019-12-01 04:06:17
I've noticed some scripts seem to be called before others on a certain page, I was wondering, what is the specific order for scripts to load? In-page before referenced .js scripts? Are they run in order from first <script> mentioned to last in page, or Is this browser-dependent? How can one make sure that a specific script is first to run in a page? I've noticed some scripts seem to be called before others on a certain page. I was wondering, what is the specific order for scripts to load? This is set by W3C in their language specifications. For the HTML 4.01 Specification , for instance, it's
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