11 lines
387 B
Markdown
11 lines
387 B
Markdown
Let's use `eval` to calculate the maths expression:
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```js demo run
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let expr = prompt("Type an arithmetic expression?", '2*3+2');
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alert( eval(expr) );
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```
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The user can input any text or code though.
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To make things safe, and limit it to arithmetics only, we can check the `expr` using a [regular expression](info:regular-expressions), so that it only may contain digits and operators.
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