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selector all is going to return the same
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thing the query selector does but
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instead of query selector returning a
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single element that matches what it
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looks for query selector all is going to
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return to me an array of all of the
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elements that match my particular query
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so if I want to select not just the
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first button I find but all of the
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buttons I find I can here say query
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selector all for button and that will
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give me back a JavaScript array the
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equivalent of a list that represents all
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of those buttons and we can actually
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test what this looks like by looking at
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things inside of the JavaScript console
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that if I go ahead and refresh this page
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colors I can open up the inspector go
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into the JavaScript console and just as
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you could see error messages here you
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can also actually write JavaScript code
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here as well so I can say something like
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document query selector button say all
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right what's going to happen when I try
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and select for a button on this
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particular page and what I get is all
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right I get just this very first button
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button whose data - color is equal to
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red that's what I would expect query
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selector just finds me one element and
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it's going to find me
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the very first element and likewise I
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can say all right
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instead of query selector let's do query
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selector all and what I get back is a
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node list which you can think of as kind
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of like an array or a list in Python
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that's got three buttons in it button 0
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1 and 2 and just as with a list in
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Python as you can index into things
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arrays and python arrays in JavaScript
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can be indexed into as well but if I
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have something like constant Eames
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equals Harry Ron and Hermione like a
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array of 3 names I can say name square
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bracket 0 to get the first name name
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square bracket 1 to get the second one
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name square bracket 2 to get the third
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one for
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example and that gives me each of the
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individual elements in the array if I
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want to get the whole length of the
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array I can do names dot lengths to get
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all right the length of the names array
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happens to be three so just some
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additional features that we have access
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to if you happen to have an array of
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things
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turns out query selector all returns to
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me a node list which is kind of like an
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array and that's going to be useful
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because when I say document query
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selector all button I am saying get me
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all of the buttons on the page and now
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what I would like to do is effectively
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loop over all of those buttons and say
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for each of the buttons inside of this
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list that comes back to me I would like
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to add an event handler for when that
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button is clicked on to say for each of
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the buttons that comes back go ahead and
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say when you're clicked on change the
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color of the h1 element and so there are
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a number of ways again that you could do
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this but one way is to use a particular
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property called for each and for each is
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a function that accepts as an argument
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another function where the idea is going
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to be I would like to run a function for
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each of the elements inside of an array
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or inside of a node list for example so
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here I can say for each button go ahead
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and run this function this is going to
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be a function now that takes something
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as input it's going to take one of the
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elements in the list as input something
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like a button and now for each button
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what would I like to do for that button
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well when the button is clicked on
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button dot on click then go ahead and
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run a function that is going to document
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query selector get me the element whose
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ID is hello change its style within the
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style change its color and what do I
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want to change its color to well I have
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access to this button this argument to
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the function is whichever button I'm
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currently trying to add an event
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listener for and in order to access its
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data properties I can access a special
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