JavaScript intensive Tutorial-using myths

This article ish5eduAgency officialHTML5 Trainingtutorials, the main introduction:JavaScript Intensive Tutorials--Use mistake

JavaScript usage Myths in this section we will discuss the pitfalls of JavaScript usage. Assignment operator Application Error in a JavaScript program if you use the equal sign (=) of the assignment operator in an IF condition statement, the correct method is to use the two equals sign (= =) of the comparison operator. The IF Condition statement returns False (as we expected) because X is not equal to 10:var x = 0;if (x = = 10)

if  conditional statement returns  true  (not what we expected) because the conditional statement executes as  x  assignment  10,10   true:var x =  0;if  (x = 10) 

The if  conditional statement returns  false  (not what we expected) because the conditional statement executes as  x  assignment  0,0   false:var x = The  0;if  (X = 0) Note Assignment statement returns the value of the variable. Common errors for comparison operators in a general comparison, the data type is ignored, and the following  if  conditional statements return  true:var x = 10;var y =  ";if " (x == y) in the strict comparison operation,===  is the identity of the operator, while checking the expression value and type, the following  if  conditional statements return  false:var  x = 10;var y = ;if  (x === y) This error often appears in the  switch  statement, The switch  statement is compared using the identity calculation character (= = =): The following instance executes  alert  popup: Var x = 10;switch (x)  {     case 10: alert ("Hello");} The following instances do not execute because of type inconsistency  alert  popup: Var x = 10;switch (x)  {    case   "Ten":  alert ("Hello");} Addition and Connection Considerations addition is two numbers added. The connection is a two-string connection. Both the addition and connection of javascript  use the  +  operator. Next we can see the difference between the number of two numbers and the connection between numbers and strings through an example:var x = 10 + 5;           // x The result is  15var x = 10 +  "5";        //  x  results for   "105" Use variable addition results also inconsistent: var x = 10;var y = 5;var z = x  + y;           // z  Results for   15var x = 10;var y =  "5";var z = x + y;            // z  results for   "105"

Click to enter JavaScript intensive tutorial

This article is from the "11721999" blog, please be sure to keep this source http://11731999.blog.51cto.com/11721999/1855287

JavaScript intensive Tutorial-using myths