--- id: 6352e93db104661305c5f658 title: Step 29 challengeType: 0 dashedName: step-29 --- # --description-- To calculate the occurrence you can use the following approach: ```js const numbersArr = [1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4]; const counts = {}; numbersArr.forEach((el) => { if (counts[el]) { counts[el] += 1; } else { counts[el] = 1; } }); ``` Check if the current number is already in the `counts` object. If it is, increment it by `1`. If it is not, set it to `1`. Resulting object. The keys are the numbers from the array and the values are the number of times each number appears in the list: ```js { 1: 3, 2: 3, 3: 3, 4: 3, 5: 2 } ``` For this step, start by declaring an empty `counts` object. Later on in the project, you will use this object to calculate the mode of the list of numbers. # --hints-- Your `getMode` function should have a `counts` variable. ```js assert.match(getMode.toString(), /counts\s*=/); ``` Your `counts` variable should be an empty object. ```js assert.match(getMode.toString(), /counts\s*=\s*\{\s*\}\s*;?/); ``` # --seed-- ## --seed-contents-- ```html Statistics Calculator

Statistics Calculator

Enter a list of comma-separated numbers.

The mean of a list of numbers is the average, calculated by taking the sum of all numbers and dividing that by the count of numbers.

Mean:

The median of a list of numbers is the number that appears in the middle of the list, when sorted from least to greatest.

Median:

The mode of a list of numbers is the number that appears most often in the list.

Mode:

The range of a list of numbers is the difference between the largest and smallest numbers in the list.

Range:

The variance of a list of numbers measures how far the values are from the mean, on average.

Variance:

The standard deviation of a list of numbers is the square root of the variance.

Standard Deviation:

``` ```css body { margin: 0; background-color: rgb(27, 27, 50); text-align: center; color: #fff; } button { cursor: pointer; background-color: rgb(59, 59, 79); border: 3px solid white; color: white; } input { background-color: rgb(10, 10, 35); color: white; border: 1px solid rgb(59, 59, 79); } .bold { font-weight: bold; } ``` ```js const getMean = (array) => array.reduce((acc, el) => acc + el, 0) / array.length; const getMedian = (array) => { const sorted = array.sort((a, b) => a - b); const median = array.length % 2 === 0 ? getMean([sorted[array.length / 2], sorted[array.length / 2 - 1]]) : sorted[Math.floor(array.length / 2)]; return median; } --fcc-editable-region-- const getMode = (array) => { } --fcc-editable-region-- const calculate = () => { const value = document.querySelector("#numbers").value; const array = value.split(/,\s*/g); const numbers = array.map(el => Number(el)).filter(el => !isNaN(el)); const mean = getMean(numbers); const median = getMedian(numbers); document.querySelector("#mean").textContent = mean; document.querySelector("#median").textContent = median; } ```