a funny take on understanding 'if statements' in javascript ? 3

[c0deM0nK424]

If I earn at least $500 this week, I can pay the electric bill; I must pay the bill, or else my lights will be
shut off."


You can generate the exact same sentiment in JavaScript using only two variables: income and lights. Presume
that the variable income has been previously assigned some numeric value representing this week's earnings.

The variable lights will be assigned on the condition of the income and will receive a Boolean value (true or false)
because there are only two possible outcomes for the lights: remain on or shut off. Given all this, the JavaScript
version of the above statement, using the JavaScript If...else construction, would look like this:


if (income >=500) {
lights = true;
else
{ lights = false;
}


Given this statement, JavaScript would first evaluate the expression (income >= 500). If this returns a true result,
JavaScript executes the statements within the first set of brackets {}. If the expression is false, JavaScript skips
ahead to the else clause and executes the statements within the set of brackets immediately below the else
keyword. You can include as many statements as you want within the brackets of a clause, but you must
remember to end each statement with a semicolon ( as in this example:

if (income >=500) {
lights = true;
savings=income-bills;


To JavaScript, the semicolon is the signal that one statement has finished and another is about to begin.

 

[ChrisHirst]

Actually the semicolon is optional in javascript and a statement will also terminate with an end of line marker (/n) so a semicolon is only required when multiple statements are on a single line.


eg:
a=1;b=2;c=3;

is syntactically and operationally identical to

a=1
b=2
c=3

Chris.

Indifference will be the downfall of mankind, but who cares?
Time flies like an arrow, however, fruit flies like a banana.
Webmaster Forum

 

[feherke]

Hi

a semicolon is only required when multiple statements are on a single line

Generally correct. Just you can not count on the interpreter to consider the same thing a single line.

Try to remove any of the semicolons here :

[b]var[/b] str [teal]=[/teal] [i][green]'test'[/green][/i]

[teal];[[/teal][i][green]'whatever'[/green][/i][teal]].[/teal][COLOR=orange]forEach[/color][teal]([/teal][b]function[/b][teal]([/teal]value[teal]) {[/teal] console[teal].[/teal][COLOR=orange]log[/color][teal]([/teal]value[teal]) })[/teal]

[teal];([/teal][b]function[/b][teal]() {[/teal] console[teal].[/teal][COLOR=orange]log[/color][teal]([/teal][i][green]'whatever'[/green][/i][teal]) })()[/teal]

( The strange placing of semicolons in such case is just a frequent habit. )


Feherke.
feherke.ga

 

[1DMF]

and there is always the ternary...

lights = (income >= 500)?true:false;

depending on the requirements of the test and assignment

"In complete darkness we are all the same, it is only our knowledge and wisdom that separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!"
Free Electronic Dance Music

 

[feherke]

Hi

Or in this extremely simple case, no ternary ;-) :

lights [teal]=[/teal] income [teal]>=[/teal] [purple]500[/purple]

To stick with the original example :

[b]var[/b] bill [teal]=[/teal] [purple]500[/purple]
[b]var[/b] income [teal]=[/teal] [highlight #9f9][purple]800[/purple][/highlight]

[teal];([/teal]light [teal]=[/teal] income [teal]>=[/teal] bill[teal]) && ([/teal]income [teal]-=[/teal] bill[teal])[/teal]

console[teal].[/teal][COLOR=orange]log[/color][teal]([/teal][i][green]'light'[/green][/i][teal],[/teal] light[teal])[/teal]     [gray]// light true[/gray]
console[teal].[/teal][COLOR=orange]log[/color][teal]([/teal][i][green]'income'[/green][/i][teal],[/teal] income[teal])[/teal]   [gray]// income 300[/gray]

[b]var[/b] bill [teal]=[/teal] [purple]500[/purple]
[b]var[/b] income [teal]=[/teal] [highlight #f99][purple]400[/purple][/highlight]

[teal];([/teal]light [teal]=[/teal] income [teal]>=[/teal] bill[teal]) && ([/teal]income [teal]-=[/teal] bill[teal])[/teal]

console[teal].[/teal][COLOR=orange]log[/color][teal]([/teal][i][green]'light'[/green][/i][teal],[/teal] light[teal])[/teal]     [gray]// light false[/gray]
console[teal].[/teal][COLOR=orange]log[/color][teal]([/teal][i][green]'income'[/green][/i][teal],[/teal] income[teal])[/teal]   [gray]// income 400[/gray]

Feherke.
feherke.ga

 

[ChrisHirst]

Generally correct. Just you can not count on the interpreter to consider the same thing a single line.

Sure however, the only time I've seen it 'broken' is when the script document has been through some sort of "white space" compression/removal tool. It is of course good practice to include the semicolons particularly if you are going to "minify" [and what a stupid 'word' that is!] or obfuscate the scripts.

Chris.

Indifference will be the downfall of mankind, but who cares?
Time flies like an arrow, however, fruit flies like a banana.
Webmaster Forum

 

[feherke]

Hi

Why would need to alter whitespaces for that ? If you remove the semicolons from my example posted at 5 Aug 15 12:54, works for you ? For me it crashes both with Gecko and WebKit.


Feherke.
feherke.ga

 

[1DMF]

nice one feherke!

Though I would write it ...

lights = (income >= 500);

To ensure precedence with parentheses, I also find it a little easier to read.

"In complete darkness we are all the same, it is only our knowledge and wisdom that separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!"
Free Electronic Dance Music