Scoping rules
The main difference is scoping rules. Variables declared by var
keyword are scoped to the immediate function body (hence the function scope) while let
variables are scoped to the immediate enclosing block denoted by { }
(hence the block scope).
function run() {
var foo = "Foo";
let bar = "Bar";
console.log(foo, bar); // Foo Bar
{
var moo = "Mooo"
let baz = "Bazz";
console.log(moo, baz); // Mooo Bazz
}
console.log(moo); // Mooo
console.log(baz); // ReferenceError
}
run();
The reason why let
keyword was introduced to the language was function scope is confusing and was one of the main sources of bugs in JavaScript.
Take a look at this example from another stackoverflow question:
var funcs = [];
// let's create 3 functions
for (var i = 0; i < 3; i++) {
// and store them in funcs
funcs[i] = function() {
// each should log its value.
console.log("My value: " + i);
};
}
for (var j = 0; j < 3; j++) {
// and now let's run each one to see
funcs[j]();
}
My value: 3
was output to console each time funcs[j]();
was invoked since anonymous functions were bound to the same variable.
People had to create immediately invoked functions to capture correct values from the loops but that was also hairy.
Hoisting
While variables declared with var
keyword are hoisted (initialized with undefined
before the code is run) which means they are accessible in their enclosing scope even before they are declared:
function run() {
console.log(foo); // undefined
var foo = "Foo";
console.log(foo); // Foo
}
run();
let
variables are not initialized until their definition is evaluated. Accessing them before the initialization results in a ReferenceError
. The variable is said to be in "temporal dead zone" from the start of the block until the initialization is processed.
function checkHoisting() {
console.log(foo); // ReferenceError
let foo = "Foo";
console.log(foo); // Foo
}
checkHoisting();
Creating global object property
At the top level, let
, unlike var
, does not create a property on the global object:
var foo = "Foo"; // globally scoped
let bar = "Bar"; // not allowed to be globally scoped
console.log(window.foo); // Foo
console.log(window.bar); // undefined
Redeclaration
In strict mode, var
will let you re-declare the same variable in the same scope while let
raises a SyntaxError.
'use strict';
var foo = "foo1";
var foo = "foo2"; // No problem, 'foo1' is replaced with 'foo2'.
let bar = "bar1";
let bar = "bar2"; // SyntaxError: Identifier 'bar' has already been declared
If you don't need the change to animate then you don't need to use any special plugins - I'd just use the native JavaScript window.scrollTo()
method -- passing in 0, 0
will scroll the page to the top left instantly.
window.scrollTo(xCoord, yCoord);
Parameters
- xCoord is the pixel along the horizontal axis.
- yCoord is the pixel along the vertical axis.
Best Answer
As far as I know the boundaries feature is not provided from the Google Map API v3 yet.
You need to know the boundaries in order to shape a polygon. The information which is returned by the Geocoder given the address in not enough to shape the boundaries. You may see the returned info here.
The Stockholm boundaries are:
'17.73966,59.66395|17.75651,59.61827|17.81771,59.58645|17.84347,59.53069|17.78465,59.49340|17.78277,59.38916|17.83277,59.36500|17.93215,59.33652|18.00736,59.34496|18.09139,59.33444|18.05722,59.39139|18.12000,59.45388|18.19508,59.45012|18.16562,59.41083|18.32826,59.39795|18.28659,59.41228|18.25945,59.44638|18.31722,59.47361|18.37333,59.46694|18.66638,59.59138|18.69979,59.64409|18.74555,59.68916|18.84139,59.71249|18.98569,59.71666|19.03222,59.71999|19.07965,59.76743|18.93472,59.78361|18.86472,59.79804|18.96922,59.86561|19.06545,59.83250|19.07056,59.88972|19.00722,59.91277|18.92972,59.92472|18.89000,59.95805|18.81722,60.07548|18.77666,60.11084|18.71139,60.12806|18.63277,60.14500|18.50743,60.15265|18.44805,59.99249|18.37334,59.86500|18.29055,59.83527|18.15472,59.79556|18.08111,59.74014|17.96055,59.70472|17.89694,59.68916|17.73966,59.66395'
In conclusion the hard part is to find the boundaries for the cities you want to get drawn on your map. I'm not sure whether there is a free service which provides these boundaries. Check this Stackoverflow question to get more information about sites which provide boundaries.
In the below example when you click the Draw Stockholm button then the Stockholm is drawn on the map.
I hope this helps.