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Number() and parseInt() are two different functions in JavaScript used to convert strings to numbers, and they have some differences in how they handle strings.

Number()#

• The Number() function converts the entire string to a number.
• If the string contains non-numeric characters (except leading spaces and signs), it returns NaN.
• If the string can be fully parsed as a number, it returns that number.

parseInt()#

• The parseInt() function parses the integer part of a string until it encounters the first non-numeric character.
• You can specify an optional radix (base) to parse the string.
• If the string starts with a non-numeric character, parseInt() returns NaN.

Example Explanation#

Example 1#

let a = "1hola1";
console.log(Number(a)); // Output: NaN
console.log(parseInt(a)); // Output: 1

Explanation:

• Number("1hola1") returns NaN because the entire string "1hola1" cannot be converted to a valid number.
• parseInt("1hola1") returns 1 because it parses from the beginning of the string until it encounters the non-numeric character h.

Example 2#

let a = "1";
console.log(Number(a)); // Output: 1
console.log(parseInt(a)); // Output: 1

Explanation:

• Both Number("1") and parseInt("1") return 1 because the string "1" is a valid number without any non-numeric characters interfering with parsing.

Summary#

• Using Number() converts the entire string to a number, returning NaN if the string contains any non-numeric characters.
• Using parseInt() parses the integer part of the string from the beginning until it encounters a non-numeric character.

Other Examples#

console.log(Number("123.45")); // Output: 123.45
console.log(parseInt("123.45")); // Output: 123

console.log(Number("   123   ")); // Output: 123
console.log(parseInt("   123   ")); // Output: 123

console.log(Number("123abc")); // Output: NaN
console.log(parseInt("123abc")); // Output: 123

console.log(Number("abc123")); // Output: NaN
console.log(parseInt("abc123")); // Output: NaN

These examples demonstrate the differences in behavior between Number() and parseInt() when handling different strings.

Learned something new again.