JavaScript/JScript: Control Structures I - Pearson Learning Solutions

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Chapter 14 JavaScript/JScript: Control Structures I 407
Most JavaScript programmers prefer to write the preceding if structure as
if ( grade >= 90 )
document.writeln( "A" );
else if ( grade >= 80 )
document.writeln( "B" );
else if ( grade >= 70 )
document.writeln( "C" );
else if ( grade >= 60 )
document.writeln( "D" );
else
document.writeln( "F" );
The two forms are equivalent. The latter form is popular because it avoids the deep indentation
of the code to the right. Such deep indentation often leaves little room on a line, forcing
lines to be split and decreasing program readability.
It is important to note that the JavaScript interpreter always associates an else with
the previous if, unless told to do otherwise by the placement of braces ({}). This is
referred to as the dangling-else problem. For example,
if ( x > 5 )
if ( y > 5 )
document.writeln( "x and y are > 5" );
else
document.writeln( "x is 5" is
output. Otherwise, it appears that if x is not greater than 5, the else part of the if/else
structure outputs the string "x is 5" );
else
document.writeln( "x is 5"—is displayed.
However, if the second condition is false, the string "x is 5" );
}
else
document.writeln( "x is