Code for "A few reasons to use Underscore.js (or Lo-Dash)"

after_chaining.js

function capAndJoinWords(aryOfWords) {
	return _.chain(aryOfWords)
		.map(function(item) { return item + '123'; })
		.map(function(item) { return item.toUpperCase(); })
		.reverse()
		.value()
		.join(' ');
}

capAndJoinWords(['array', 'this', 'in', 'are', 'words', 'test']); // "TEST123 WORDS123 ARE123 IN123 THIS123 ARRAY123"

after_tap.js

function somethingImporatant() {
	return _.tap(this.getObject(), function(obj) {
		obj.val = "Value";
		doSomething(obj);	
	});
}

after_utilities.js

function doAThing(boolArg) {
	if (!_.isUndefined(boolArg) && !boolArg) {
		// This would fire only if boolArg was sent something, and that something was falsy
	}
}

before_chaining.js

function capAndJoinWords(aryOfWords) {
	var result = [];
	
	if (aryOfWords.length) {
		for (i = aryOfWords.length - 1; i >= 0; i--) {
			result.push((aryOfWords[i] + '123').toUpperCase());
		}
	}
	
	return result.join(' ');
}

capAndJoinWords(['array', 'this', 'in', 'are', 'words', 'test']); // "TEST123 WORDS123 ARE123 IN123 THIS123 ARRAY123"

before_tap.js

function somethingImporatant() {
	var tmp = this.getObject();
	
	tmp.val = "Value";
	doSomething(val);
	
	return tmp;
}

before_utilities.js

function doAThing(boolArg) {
	if (!boolArg) {
		// This would fire if boolArg was never sent or was sent with "false"
	}
}

custom_mixin.js

_.mixin({
	dumbify: function(items) {
		return _.chain(items)
			.map(function(item) { return item + '123'; })
			.map(function(item) { return item.toUpperCase(); })
			.reverse()
			.value();
	}
});

function capAndJoinWordsDirectly(aryOfWords) {
	return _.dumbify(aryOfWords).join(' ');
}

capAndJoinWordsDirectly(['array', 'this', 'in', 'are', 'words', 'test']); // "TEST123 WORDS123 ARE123 IN123 THIS123 ARRAY123"

custom_mixin_chain.js

_.mixin({
	dumbify: function(items) {
		return _.chain(items)
			.map(function(item) { return item + '123'; })
			.map(function(item) { return item.toUpperCase(); })
			.reverse()
			.value();
	}
});

function capAndGetLastWord(aryOfWords) {
	return _.chain(aryOfWords)
		.dumbify()
		.first()
		.value();
}

capAndGetLastWord(['array', 'this', 'in', 'are', 'words', 'test']); // "TEST123"

defaults_naive.js

function doAthing(obj, params) {

	if (params && params.something) {
		// Do something here
	}
	
	if (params && params.somethingElse && params.somethingElse === 'some_value') {
		// Do another thing
	}
	
	// Repeat every time you need to look at one params value
}
 
doAThing(123, {
	something: 'new',
})

defaults_new.js

function doAthing(obj, params) {
	params || (params = {});
	
	_.defaults(params, {
		something: 'thing',
		somethingElse: 'else',
		oneMore: 'this'
	})
	
	console.log(params) // { something: 'new', somethingElse: 'else', oneMore: 'this' }
}

doAThing(123, {
	something: 'new',
})

defaults_old.js

function doAthing(obj, params) {
	params || (params = {});
	
	if (!params.something)
		params.something = 'thing';
	if (!params.somethingElse)
		params.somethingElse = 'else';
	if (!params.oneMore)
		params.oneMore = 'this';
	
	console.log(params) // { something: 'new', somethingElse: 'else', oneMore: 'this' }
}

doAThing(123, {
	something: 'new',
})