Sep 15, 2026 · 4 min · 4 segments
THEORETICAL RECAP In JavaScript ES6+, an array is an ordered collection of values that you can traverse and transform. To compute statistics, you rely on a small set of core tools. A variable declared…
Theoretical recap.
In JavaScript ES6+, an array is an ordered collection of values that you can traverse and transform.
To compute statistics, you rely on a small set of core tools.
A variable declared with const or let holds your data.
A function encapsulates a reusable calculation and returns a result.
To iterate over grades, you can use a classic for loop or, more idiomatically in ES6, array methods such as forEach, reduce, filter, map, Math.min, and Math.max. A clear mental model: treat your grade list as raw material that passes through a pipeline of small functions, each producing one clean number: sum, average, minimum, maximum, count above a threshold.
Common mistakes include forgetting the initial value of reduce, start the accumulator at zero, dividing by zero when the array is empty, comparing strings instead of numbers because values came from text input, and mutating the original array by accident.
Always convert with Number or parseInt when reading DOM values.
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Theoretical recap.
In JavaScript ES6+, an array is an ordered collection of values that you can traverse and transform.
To compute statistics, you rely on a small set of core tools.
A variable declared with const or let holds your data.
A function encapsulates a reusable calculation and returns a result.
To iterate over grades, you can use a classic for loop or, more idiomatically in ES6, array methods such as forEach, reduce, filter, map, Math.min, and Math.max. A clear mental model: treat your grade list as raw material that passes through a pipeline of small functions, each producing one clean number: sum, average, minimum, maximum, count above a threshold.
Common mistakes include forgetting the initial value of reduce, start the accumulator at zero, dividing by zero when the array is empty, comparing strings instead of numbers because values came from text input, and mutating the original array by accident.
Always convert with Number or parseInt when reading DOM values.