Salesforce.com: Expression Functions in Salesforce lightning

Generally In every component implementation we have a need to  change the UI conditionally, or show/hide a section/column based on certain conditions. We need simple ways to do this instead of having every handler in code. Below are key operators and their syntax to handle any such situation

Math Functions

The math functions perform math operations on numbers. They take numerical arguments. The Corresponding Operator column lists equivalent operators, if any.
Function Alternative Usage Description Corresponding Operator
add concat add(1,2) Adds the first argument to the second. +
sub subtract sub(10,2) Subtracts the second argument from the first. –
mult multiply mult(2,10) Multiplies the first argument by the second. *
div divide div(4,2) Divides the first argument by the second. /
mod modulus mod(5,2) Returns the integer remainder resulting from dividing the first argument by the second. %
abs
abs(-5) Returns the absolute value of the argument: the same number if the argument is positive, and the number without its negative sign if the number is negative. For example, abs(-5) is 5. None
neg negate neg(100) Reverses the sign of the argument. For example, neg(100) is -100. – (unary)

String Functions

Function Alternative Usage Description Corresponding Operator
concat add concat(‘Hello ‘, ‘world’)
add(‘Walk ‘, ‘the dog’)
 Concatenates the two arguments. +
format
format($Label.ns.labelName, v.myVal)
This function works for arguments of type String, Decimal, Double, Integer, Long, Array, String[], List, and Set.
 Replaces any parameter placeholders with comma-separated attribute values.
join
join(separator, subStr1, subStr2, subStrN)
join(‘ ‘,’class1’, ‘class2’, v.class)
 Joins the substrings adding the separator String (first argument) between each subsequent argument.

Label Functions

Function Usage Description
format format($Label.np.labelName, v.attribute1 , v.attribute2)
format($Label.np.hello, v.name)
 Outputs a label and updates it. Replaces any parameter placeholders with comma-separated attribute values. Supports ternary operators in labels and attributes.

Informational Functions

Function Usage Description
length myArray.length Returns the length of an array or a string.
empty empty(v.attributeName)

This function works for arguments of type String, Array, Object, List, Map, or Set.
 Returns true if the argument is empty. An empty argument is undefined, null, an empty array, or an empty string. An object with no properties is not considered empty.

{! !empty(v.myArray)} evaluates faster than {!v.myArray && v.myArray.length > 0} so we recommend empty() to improve performance.
The $A.util.isEmpty() method in JavaScript is equivalent to the empty() expression in markup.

Comparison Functions

Comparison functions take two number arguments and return true or false depending on the comparison result. The eqand ne functions can also take other data types for their arguments, such as strings.
Function Usage Description Corresponding Operator
equals equals(1,1) Returns true if the specified arguments are equal. The arguments can be any data type. == or eq
notequals notequals(1,2) Returns true if the specified arguments are not equal. The arguments can be any data type. != or ne
lessthan lessthan(1,5) Returns true if the first argument is numerically less than the second argument. < or lt
greaterthan greaterthan(5,1) Returns true if the first argument is numerically greater than the second argument. > or gt
lessthanorequal lessthanorequal(1,2) Returns true if the first argument is numerically less than or equal to the second argument. <= or le
greaterthanorequal greaterthanorequal(2,1) Returns true if the first argument is numerically greather than or equal to the second argument. >= or ge

Boolean Functions

Boolean functions operate on Boolean arguments. They are equivalent to logical operators.
Function Usage Description Corresponding Operator
and and(isEnabled, hasPermission) Returns true if both arguments are true. &&
or or(hasPermission, hasVIPPass) Returns true if either one of the arguments is true. ||
not not(isNew) Returns true if the argument is false. !

Conditional Function

Function Usage Description Corresponding Operator
if if(isEnabled, ‘Enabled’, ‘Not enabled’)   



Source : http://www.saasanalogy.com/conditional-functions-in-salesforce-lightning/

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