**Assign and evaluate**

if ( x = y + z ) { alert( "true" ); }

Assigns x to the sum of y and z and evaluates the result.

**Compare (irrespective of data type)**

if ( x == y + z ) { alert( "true" ); }

The result of the sum of y and z is compared to x where both sides must have the same value.

Example:

x = "5"

y = 10

z = -5

y + z = 5

Using the above values, the condition will be considered to be true because the sum of y and z is converted to a string prior to the comparison.

**Compare and match data types**

if ( x === y + z ) { alert( "true" ); }

The result of the sum of y and z is compared to x where both sides must have the same value and be of the same data type.

To summarise, always use === when doing conditional statements unless you want to compare values of different data types.

* zero and an empty string are considered to be false and all other numbers and strings are considered to be true.

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