In the last article, we looked at hoisting, prototypal inheritance, and the differences between an attribute and a property. You can find that article here. Today, we will continue to prepare for an interview by looking at the differences between postfix and prefix increment/decrement operators, truthy and falsy values, and equality vs. identity operators.
Postfix & Prefix Increment/Decrement Operators
Postfix (x++
/x--
) and prefix (++x
/--x
) increment/decrement operators are used to either increase or decrease a variable by 1 and return that value. Most of us are familiar with the postfix increment operator i++
found in a For Loop. So if they both increase or decrease a variable by one, what's the difference?
If it is used postfix (x++
/x--
), then it returns the value before incrementing or decrementing the variable. Check out this example:
If it is used prefix (++x
/--x
), it returns the value after incrementing or decrementing the variable. Check out this example:
Truthy & Falsy Values
Truthy and falsy are funny sounding words. But, what are they? JavaScript uses type coercion, in a boolean context, on all values. When a value is evaluated in a boolean context, if the value is true it is called a truthy and if it is false it is called a falsy. All values are considered truthy, except for false
, 0
, empty strings (single quotes, double quotes, and template literals), null
, undefined
, and NaN
, which are all falsy.
Equality vs. Identity Operators
So what's the difference between ==
and ===
? The equality operator (==
) compares two values for equality after any necessary type conversion. So 1 == "1"
would return true
, just the same as 1 == 1
returns true. JavaScript converts the string "1"
into a number and then compares it to the number 1
.
The identity or strict equality operator (===
) compares two values for equality, but there is no type conversion. So the values have to be of an equal type also. So 1 === 1
would return true
, whereas 1 === "1"
would return false
.
I hope that this article has helped you to better understand postfix and prefix operators, truthy and falsy, and the equality and identity operators. I would like to thank all of my readers for the overwhelming support of my first article on Dev.to. I would also like to thank my instructors, Jerome Hardaway, Brad Hankee, and Phil Tenteromano, over at #Vets Who Code for their training, support, and for pushing me to write articles. I wish you all the best of luck on your interviews and stay tuned for more articles in the series over the next few weeks.
Top comments (0)