Walking

function walking(input) {
    let stepSum = 0;
    for (let i = 0; i < input.length; i++){
        if (input[i] !== "Going home"){
            stepSum += Number(input[i]);
        }
    }
    if (stepSum < 10000) {
        console.log(`${10000 - stepSum} more steps to reach goal.`);
    } else {
        console.log(`Goal reached! Good job!`);
    }
    return;
}

Решение с тернарен оператор:

function walking(input) {
    let stepSum = 10000;
    for (let i = 0; i < input.length; i++) {
        stepSum -= input[i] !== "Going home" ? Number(input[i]) : 0;
    }
    console.log(stepSum > 0 ? `${stepSum} more steps to reach goal.` :
        `Goal reached! Good job!`);
    return;
}

Или с while():

function walking(input) {
    stepSum = 10000;
    while (stepSum > 0) {
        if (input[0] === "Going home"){
            stepSum -= Number(input[1]);
            break;
        }
        stepSum -= Number(input.shift());
    }
    console.log(stepSum > 0 ? `${stepSum} more steps to reach goal.`
    : `Goal reached! Good job!`);
    return;
}