Home

Javascript Tutorial: Testing and Comparing Variables     THE if KEYWORD The if keyword is one that you will use over and over again in Javascript. It is used to test and/or compare a variable. Lets get to the example.      var name = 'John';      if (name == 'Bob') document.write('Bob Curtis'); I admit, this isn't a very practical use for the script. The statement is basically saying if name equals Bob write Bob Curtis. But analyze the parts of the script, the name variable, the if keyword, the parentheses, the variable to be tested (name) the == operator, the string used to test the variable, and what to do if the statement is true. OPERATORS Operators are used to compare variables (such as the == operator above); they consist of two groups, conditional and logical. Conditional Conditional operators are the syntax used to compare the two variables. == is equal to != is not equal to < is less than <= is less than or equal to > is greater than >= is greater than or equal to Logical Logical operators are the operators you use if you want to compare more than two variables. && and || or Just to give you an idea of how logical operators work, check out the syntax below.       THE else KEYWORD If you are using several if statements to test the same variable and you want to include a choice that will be executed if none of the previous statements are true, you should use the else keyword.      if (name == 'Bob') document.write('Bob Curtis');      else if (name == 'Sue') document.write('Sue Jones');      else document.write('John Smith'); The above statements would check to see if name equalled Bob and because it didn't it checked to see if name equalled Sue, if it reaches the else keyword and none of the above if statements have been true Javascript executes whatever is after the else keyword. Variables, Strings and Arrays (continued) Tutorial Index Testing and Comparing Variables (continued)

Sponsors

Home