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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"
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JavaScript intensive Tutorial-using myths