const now = 2037;
const ageEke = now - 1997;
const ageSarah = now - 2018;
console.log(now - 1997 > now - 2018);Operator precedence is a collection of rules in JavaScript that reflect conventions about which procedure to perform first in a given mathematical expression.
Operators with higher precedence will be executed before the lower ones.
Let's take a look at the precedence of different operators from MDN.
Image Credit: MDN DOCS
Now we can use this table to understand the precedence of the operators in the code above and how it was executed.
On the table, subtraction - has a higher precedence than greater than > which is why the numbers were executed first before making the comparison.
On the table, we can also see which operators are executed from left to right.
For Example.
console.log(25 - 10 - 5);Since subtraction is executed from left to right, the result of this calculation would be 10
let x, y; // Declare two variables in one line
x = y = 25 - 10 - 5; // x = y = 10. y = 10, x = 10
conslole.log(x, y);The result in the above example would be 10, 10.
This is because JavaScript will look at the calculation and run the ones with the higher precedence (in this case -) first before the assignment operator (=).
const averageAge = ageEke + ageSarah / 2;
console.log(ageEke, ageSarah, averageAge);Here we are calculating the average value of ageEke & ageSarah and dividing it by 2
Result would be: 40 19 49.5