convert string to a number in javascript

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I want to parse a user input which contains longitude and latitude. What I want to do is to coerce a string to a number, preserving its sign and decimal places. But what I want to do is to display a message when user's input is invalid. Which one should I follow

parseFloat(x)

second

new Number(x)

third

~~x

fourth

+x
4 Answers
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