text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
that element that we have found and to | 1,231.46 | 4.38 |
do that we can store an element inside | 1,233.77 | 3.72 |
of a variable in the same way that a | 1,235.84 | 3.72 |
variable can store a number like a | 1,237.49 | 4.35 |
counter or a string like hello world it | 1,239.56 | 4.68 |
can also store other values like an HTML | 1,241.84 | 5.04 |
element that we get back from document | 1,244.24 | 4.77 |
dog query selector so I could say | 1,246.88 | 6.54 |
something like let heading we're heading | 1,249.01 | 6.63 |
is just the name of a variable the equal | 1,253.42 | 5.85 |
to document query selector h1 for | 1,255.64 | 5.94 |
instance find the h1 element save it | 1,259.27 | 3.84 |
inside of a variable called heading and | 1,261.58 | 4.32 |
now rather than document query selector | 1,263.11 | 4.83 |
each one all the time I can just say if | 1,265.9 | 4.23 |
the headings inner HTML is hello | 1,267.94 | 4.98 |
then set the headings inner HTML to good | 1,270.13 | 3.21 |
bye | 1,272.92 | 2.91 |
otherwise I set the headings inner HTML | 1,273.34 | 3.51 |
to hello | 1,275.83 | 2.46 |
so I've improved the efficiency of the | 1,276.85 | 3.36 |
program but also reduce the number of | 1,278.29 | 3.36 |
characters of code that I've had to | 1,280.21 | 3 |
write my lines are now much shorter a | 1,281.65 | 3.39 |
little bit easier to read this we would | 1,283.21 | 4.11 |
consider to be an improvement in design | 1,285.04 | 4.17 |
and it turns out there's one other | 1,287.32 | 4.47 |
improvement we can make here too that we | 1,289.21 | 4.74 |
can define a variable like let something | 1,291.79 | 4.11 |
equal something else but it turns out | 1,293.95 | 3.48 |
that JavaScript gives us a couple of | 1,295.9 | 4.14 |
ways to define a variable and if we're | 1,297.43 | 4.56 |
going to be creating a variable whose | 1,300.04 | 4.38 |
value is never going to change we're | 1,301.99 | 4.26 |
never going to reassign the variable | 1,304.42 | 4.17 |
name to something else then instead of | 1,306.25 | 4.62 |
let we can enforce that it's never going | 1,308.59 | 5.31 |
to change by calling it a Const variable | 1,310.87 | 5.91 |
so Const heading equals document query | 1,313.9 | 5.31 |
selector h1 means I am going to create a | 1,316.78 | 4.44 |
variable called heading setting it equal | 1,319.21 | 4.35 |
to the result of document query selector | 1,321.22 | 5.82 |
h1 and never again will I change what | 1,323.56 | 5.1 |
heading is equal to I will never have | 1,327.04 | 3 |
another line of code that says heading | 1,328.66 | 3.63 |
equals something else because it is | 1,330.04 | 3.87 |
constant and JavaScript will then | 1,332.29 | 3.27 |
enforce that this variable should not | 1,333.91 | 3.72 |
change and if ever I do try to change it | 1,335.56 | 3.66 |
javascript will give me an error and | 1,337.63 | 3.84 |
this can just be helpful to prevent | 1,339.22 | 4.14 |
against possible unintended behavior | 1,341.47 | 3.81 |
that if you know you have a variable it | 1,343.36 | 3.69 |
is never going to change it's often good | 1,345.28 | 4.71 |
designed to label it as a constable so | 1,347.05 | 4.29 |
that you and other people looking at | 1,349.99 | 1.75 |
your code | 1,351.34 | 2.41 |
know that that is never going to have a | 1,351.74 | 5.25 |
value that gets changed later on so this | 1,353.75 | 5.7 |
then will behave the same way where it | 1,356.99 | 4.38 |
says hello but I can toggle it back and | 1,359.45 | 4.74 |
forth changing it to goodbye and then | 1,361.37 | 5.67 |
changing it back to hello again and so | 1,364.19 | 4.83 |
now using this ability this ability to | 1,367.04 | 4.019 |
manipulate the dawn we can go back to | 1,369.02 | 4.02 |
our counter program and actually improve | 1,371.059 | 4.471 |
upon it that right now the counter | 1,373.04 | 5.28 |
program I count and it displays an alert | 1,375.53 | 4.59 |
that says 1 I count and it displays an | 1,378.32 | 3.9 |
alert that says 2 I can probably do a | 1,380.12 | 4.23 |
little bit better than that by instead | 1,382.22 | 4.11 |
of displaying an alert actually | 1,384.35 | 4.86 |
manipulating the Dom in some way that I | 1,386.33 | 4.86 |
would like to have this h1 this big | 1,389.21 | 3.81 |
heading at the top instead of starting | 1,391.19 | 3.989 |
up by saying hello let's have it start | 1,393.02 | 5.25 |
out by saying 0 for example just some | 1,395.179 | 5.821 |
initial value for the counter and now | 1,398.27 | 4.26 |
when I increment the value of counter | 1,401 | 3.63 |
rather than display an alert that just | 1,402.53 | 3.779 |
tells me the value of the counter in an | 1,404.63 | 4.26 |
alert I'm going to instead say document | 1,406.309 | 7.671 |
query selector h1 . innerhtml | 1,408.89 | 10.05 |
equals counter where i'm saying find the | 1,413.98 | 7.42 |
h1 element updated innerhtml | 1,418.94 | 4.8 |
set it equal to whatever the value of | 1,421.4 | 5.1 |
the variable counter happens to be such | 1,423.74 | 4.86 |
that now if i refresh this page the | 1,426.5 | 3.96 |
value of this h1 initially is 0 that's | 1,428.6 | 3.66 |
the initial value but every time I click | 1,430.46 | 4.05 |
count we're going to update the contents | 1,432.26 | 4.26 |
of that h1 element and this time setting | 1,434.51 | 5.22 |
it to 1 2 3 4 and so forth every time I | 1,436.52 | 4.74 |
click the count button it's going to | 1,439.73 | 3.18 |
increment the value of the variable as | 1,441.26 | 3.93 |
well as manipulate the Dom actually | 1,442.91 | 5.82 |
making changes in order to produce the | 1,445.19 | 5.489 |
effect that I want to see on this actual | 1,448.73 | 5.07 |
page and we can begin to add additional | 1,450.679 | 4.861 |
logic to this as well maybe I do | 1,453.8 | 3.78 |
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