计算序列从一个值变为另一个值的次数

Question

I have the following sequential array where a car changes colour. It starts red and is now yellow in the below example.

A = [red,blue,yellow,red,blue] 

I need to output is the number of times it went from each colour to each other colour.

output:

red-blue:2
blue-yellow:1
yellow-red:1

Can this be done in JS? Any help greatly appreciated!

Answer 1

 function getColorChangeAmounts(colorChanges){ const colorChangesMap = {}; for(let i = 1; i < colorChanges.length; i++){ const previous = colorChanges[i - 1]; const current = colorChanges[i]; const colorChangeText = previous + "-" + current; const currentCount = colorChangesMap[colorChangeText] || 0; colorChangesMap[colorChangeText] = currentCount + 1; } return colorChangesMap; } const A = ["red", "blue", "yellow", "red", "blue"]; const colorChangesMap = getColorChangeAmounts(A); console.log("output:"); console.log(); console.log(Object.entries(colorChangesMap).map(([key, value]) => key + ":" + value).join("\n"))