编辑代码

function calc(left, right, rule) {
    switch (rule){
        case '+': 
            return left + right;
        case '-':
            return left - right;
        case '*':
            return left * right;
        case '/':
            return left / right;
    }
}
function calcExpress(arr) {
    const stack = [];
    for(let e of arr) {
        if('+-*/'.includes(e)) {
            const right = stack.pop();
            const left = stack.pop();
            const res = calc(left, right, e);
            stack.push(res);
        }else {
            stack.push(e);
        }
    }
    return stack.pop();
}
const arr = [1, 3, '+', 4, '*', 5, '-']
const res = calcExpress(arr);
console.log(res)