JavaScript, like it or not, has become the most important language on the web. Nearly every developer who builds Internet apps has to use it. But JavaScript can be tough to write and even tougher to read. So here are ten tips to help you get groovy with JavaScript.
2. Who am I?
Hi, I’m Troy. I have been developing software for over 30
years. For the last 10 years I have been focused on web,
mobile web, and mobile development. I currently work at
Kelley Blue Book as a senior software engineer. My
opinions are my own.
I can be reached rockncoder@gmail.com
Thursday, July 25, 13
3. The Rock n Coder
• http://therockncoder.blogspot.com
• http://www.youtube.com/user/rockncoder
• https://github.com/Rockncoder
• http://www.slideshare.net/rockncoder
Thursday, July 25, 13
14. Use Protection
• The Browser is a very dirty environment
• Protect your code by wrapping it in a
function
/* using protection */
(function (doc, win) {
/* put all of your precious code here to keep it safe */
/* extra bonus, parameters passed in become local, minor performance boost */
}(document, window));
Thursday, July 25, 13
16. debugger is your friend
• At times it can be difficult to set a
breakpoint
• The debugger statement allows you to set
a breakpoint any where you like
app.post("/clientadmin", function (req, res) {
var clientId = req.body.client;
console.log("/clientadmin POST: " + JSON.stringify(req.body));
if (clientId) {
mongodb.getClientModel().findOne({_id: clientId }, function (err, client) {
mongodb.getCampaignModel().find({clientId: clientId}, function (err, campaigns) {
debugger;
console.log("Campaigns: " + JSON.stringify(campaigns));
/* set the client id */
res.cookie('clientId', clientId);
res.cookie('client', JSON.stringify(client));
res.render("clientadmin.hbs", {client: client, campaigns: campaigns, user: extractUser(res)});
});
});
}
});
Thursday, July 25, 13
19. Always Use ===
• Double equals (==) does automatic type
conversion
• The results of this conversion is not logical
or obvious
• Avoid this by using triple equals (===)
• There is no good reason to ever use ==
• Same goes for !=
Thursday, July 25, 13
21. Learn to Love Falsey
• When coming from C# or Java it is
tempting to use C-like conditionals
• JavaScript conditionals can be more
succinct and performant
1 /* C-style conditional */
2 if (val != null && val.length > 0){
3 ...
4 }
5
6 /* JavaScript style conditional */
7 if (val) {
8 ...
9 }
10
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26. Getting a default value
• At times it is nice to have a default value
• JavaScript has a kind of default value operator
/* Conversions */
var defaultValue = defaultValue || 16;
var defaultString = inputValue || “Here is the default value”;
console.log(defaultValue);
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28. To Binary
• Double exclamation (!!) converts a value to
its boolean representation (true/false)
/* convert to boolean */
var toBinary = !!null;
console.log(toBinary);
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30. To Number
• The plus sign (+) before a numeric string
converts it to a numeric value
/* convert to number */
var toNumber = +"42";
console.log(toNumber);
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36. jQuery Isn’t Always the
Answer
• For many tasks plain JavaScript is better
than jQuery
• For example, finding an element by its id,
jQuery calls document.getElementById()
/* get element by Id is faster than... */
var el = document.getElementById("myDiv");
/* $('#myDiv'), which calls it */
var $el = $('#myDiv').eq(0);
Thursday, July 25, 13
38. Cache Selectors
• jQuery Selectors are method calls, not
operators
• The method calls interrogate the DOM
• Method calls are slow
• Interrogating the DOM isVERY slow
• Caching selectors can dramatically improve
the speed of your code
Thursday, July 25, 13
39. Cache Selectors
/*
jQuery Demo
*/
RocknCoder.plugInSlow = function() {
var i, val;
for(i=0; i < 50; i++) {
val = $('#styleMe').html();
}
}
RocknCoder.plugInFast = function() {
var i, val, $styleMe = $('#styleMe');
for(i=0; i < 50; i++) {
val = $styleMe.html();
}
}
Thursday, July 25, 13
41. Use
event.preventDefault
• If your code completely handles an event,
you should be sure to event.preventDefault
• This will stop unnecessary code from
executing
$('#usRank').on('click', function(evt){
evt.preventDefault();
showChart('US Rank', filterUSRank);
});
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42. Summary
• JavaScript is the most important language of
web development
• But it is a quirky language
• Use these tips to speed up your code
• And make your JavaScript code groovier
Thursday, July 25, 13