slggs/javascript-notes.txt at master · jakepearse/slggs · GitHub

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// is a single line comment

/* */ is a multi line comment but it is unsafe because the */ pair may occur in a regex

reserved names -- not all of these are actually used, but you can't use any of them;
    break
    case
    class
    catch
    const
    continue
    debugger
    default
    delete
    do
    else
    export
    extends
    finally
    for
    function
    if
    import
    in
    instanceof
    let
    new
    return
    super
    switch
    this
    throw
    try
    typeof
    var
    void
    while
    with
    yield

strings can be created using single or double quotes, there is no char type.
Two strings with the same charecters in the same order have the same value;
"foo" === "f" + "o" + "o";
strings all have a length property
"nine".length === 4;
strings have methods
"foo".toUpperCase() === "FOO";

all numbers are 64-bit floating point numbers 1 and 1.0 are the same value

declare variables with the var keyword, var age = 99;
All variables are thrown together in the global namespace... this is a serious problem with JavaScript, blocks of code {} also dont have local namespaces, even though they definately should.
Thankfully functions have a local scope, you'll want to get used to taking advantage of this fact early on.
If you foolishly declare a varibale without using the var keyword it will be thrown into the global namespace... don't do this.

comparison operators:
<
=<
>
=>
===
!==

== and != are unreliable because of 'type coersion' always use === and !==

falsey values:
There are rather many values that evalute to false;
false
null
undefined
the empty string '' or ""
the number 0
the number NaN

all other values are truthy, including true, the string "false" and all objects.

selection:
JavaScript has all the usual suspects
if (condition1) {
   // do stuff
} else if (condition2) {
  // do other stuff
} else {
  // last resort
}

switch (variable) {
 case "foo":
      statements;
      break;
 case "bar":
      statements;
      break;
 case "baz":
      statements;
      break;
 default:
      statements;
}

loops:
c style do .. while and for loops

while ( condition ) {
  // keep doing things
  }

for (var i = 0; i < someLimit; i++) {
    //do something someLimit many times
}