calculate arithmetic expression

Question

In 119. create a tokenizer, you are able to extract the tokens from a string with invalid spaces.

Now please calculate() the result of the string. You can use the tokenizer you wrote before.

calculate('1 * (20 -   300      ) ')
// -280

calculate('     1/0 ')
// Infinity

1. the input expression is syntactically valid, containing non-negative integers, +, -, *, /, (, ) and spaces
2. Don't use eval()

Code

/**
 * @param {string} str
 * @returns {Number}
 */
function calculate(str) {
  // your code here
}

Source

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