What does a + before a string means in javascript - Stack Overflow

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There is a line of code in angular2.

this.id = +this.route.snapshot.params['id'];

What is the "+" means before "this.route.snapshot.params['id']"?

I also see "+" added before a folder name such as "+detail" in angular2-webpack-starter.

Do they have the same meaning?

There is a line of code in angular2.

this.id = +this.route.snapshot.params['id'];

What is the "+" means before "this.route.snapshot.params['id']"?

I also see "+" added before a folder name such as "+detail" in angular2-webpack-starter.

Do they have the same meaning?

• javascript

Share Follow edited Mar 7, 2017 at 22:19 georgeawg 49k1313 gold badges7777 silver badges9898 bronze badges asked Mar 7, 2017 at 21:11 HenryHenry 17322 silver badges1010 bronze badges 1

• 2 + is used for a quick changing type of number-ish strings into number, e.g. +"5" will return 5. – kind user Commented Mar 7, 2017 at 21:14

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2 Answers 2

Sorted by: Reset to default 11

Using + in Javascript is a quick way to cast a string to a number as long as the string is already in the form of an integer or float.

+'5000' // yields 5000
+'2.5'  // yields 2.5

If the string contains any character that is not an integer (or decimal in the case of a float), this method will return NaN.

+'5n'  // yields NaN
+'abcd'  // yields NaN

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In short if you put + operator in front of string which contains Number then always get number other than that you will get NaN.

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