Talk:JavaScript syntax: Difference between revisions

Revision as of 03:16, 25 March 2020

Revision as of 18:45, 11 May 2020

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Should it not be explained that the following:

<sourcesyntaxhighlight lang="JavaScript">

if(x==1){

something()

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somethingelse();

}

</syntaxhighlight>

</source>

the else if works like a shorthand if (without {})

<sourcesyntaxhighlight lang="JavaScript">

if(x==1)

do something here

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}

}

</syntaxhighlight>

</source>

Sorry if that didn't make sense, I find it hard to explain.

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== For loop: end-condition? ==

<sourcesyntaxhighlight lang="JavaScript">

for (initial;end-condition;loop statement) {

/*

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*/

}

</syntaxhighlight>

</source>

The condition should be called ''while-condition'', or just ''condition'', but never ''end-condition''. As in every C-like language, the for{} loop cycles '''while''' the condition is satisfied. --[[User:Comocomocomocomo|Como]] ([[User talk:Comocomocomocomo|talk]]) 14:28, 23 October 2008 (UTC)

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The code could be changed to also illustrate the ternary operator <tt>? :</tt> :

<sourcesyntaxhighlight lang="JavaScript">

return diff > 0 ? gcd(segmentB, diff) : gcd(segmentA, -diff)

</syntaxhighlight>

</source>

Since the code might be copied, it would be well to change it, after testing, to the more efficient method, in which the second argument to the internal <tt>gcd</tt> is either <tt>A mod B</tt> or <tt>B mod A</tt>, which is approximately equally easy to read; or to the wondrous non-recursive form :

<sourcesyntaxhighlight lang="JavaScript">

function GCD(U, V) { // or HCF

while (true) {

if (!(U %= V)) return V

if (!(V %= U)) return U } }

</syntaxhighlight>

</source>

And, for the same reason, the alternative acronym HCF should be included. [[Special:Contributions/82.163.24.100|82.163.24.100]] ([[User talk:82.163.24.100|talk]]) 20:01, 24 July 2009 (UTC)

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<div style="font-size:75%;line-height:150%;margin-left:2.5em;padding-bottom:1.5em;">

<sourcesyntaxhighlight lang="JavaScript">

// Automatic type coercion

//Boolean operands will be converted to a number, if possible, or to a string (if the other is a string)

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alert(true === 1); // false

alert(true === "1"); // false

</syntaxhighlight>

</source>

Examples with "falsy" and "truthy" values.

<sourcesyntaxhighlight lang="JavaScript">alert(3?true:false); // true

alert(true == 3); // false

// 3 is logically true(known as "truthy"), as are all non-0 non-nan numbers. However, it is not "true", even with type coercion.

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alert(false == +'NaN'); // false (shorthand for getting a NaN value)

</syntaxhighlight>

</source>

</div>

:I think some of the permutations could potentially be eliminated but it's necessary to show, for example, that neither <code>true==2</code> nor <code>false==2</code> behave the way one might expect.

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== Function example code misleading ==

<sourcesyntaxhighlight lang="JavaScript">

var obj1 = {a : 1};

var obj2 = {b : 2};

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foo(obj1, 3); // Does not affect obj1 at all. 3 is additional parameter

alert(obj1.a + " " + obj2.b); // writes 1 3

</syntaxhighlight>

</source>

This is misleading because obj1 can be modified by the function. It is quite odd (in an explanation) to pass a parameter to a function and then ignore it.

Consider:

<sourcesyntaxhighlight lang="JavaScript">

var obj1 = {a : 1};

var obj2 = {b : 2};

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foo(obj1, 3); // Does affect obj1. 3 is additional parameter

alert(obj1.a + " " + obj2.b); // writes 7 3

</syntaxhighlight>

</source>

Because the object parameter is passed by reference it can be modified.

This is OR for me. I am just learning. But I was surprised that obj1 can be modified in the function, by p.a=7, yet p=obj2 does not affect obj1. This should be explained. [[User:QuentinUK|QuentinUK]] ([[User talk:QuentinUK|talk]]) 02:27, 28 June 2011 (UTC)

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The following

<sourcesyntaxhighlight lang="JavaScript">

alert( !0 === Boolean( !0 ) === !!1 === Boolean( 1 ) === true );

alert( !!0 === Boolean( 0 ) === !1 === Boolean( !1 ) === false );

alert( !"" === Boolean( !"" ) === !!"s" === Boolean( "s" ) === true );

alert( !!"" === Boolean( "" ) === !"s" === Boolean( !"s" ) === false );

</syntaxhighlight>

</source>

Gives the impression that equality can be chained together. A===B===C being true when they are all equal, this is not the case. [[User:QuentinUK|QuentinUK]] ([[User talk:QuentinUK|talk]]) 10:57, 11 August 2011 (UTC)