There are several ways you can convert
Typescript String
to
Number
. The best way is to make use of the
unary plus
+
operator or the
Number
global function. You can make use of the
parseint
or
parsefloat
functions. The following examples show how to make use of these functions.
Table of Contents
Unary plus (+)
The
Unary plus
(+) operator converts all string representations of numbers, boolean values(true and false), and null to numbers. If the operand cannot be converted into a number, the unary plus operator will return
NaN
.
The following are some of the examples
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console
.
log
(
+
"100"
)
//100
console
.
log
(
+
"100.5175"
)
//100.5175
console
.
log
(
+
"10AA0.5175"
)
//NaN
console
.
log
(
+
""
)
//0
console
.
log
(
+
" "
)
//0
console
.
log
(
+
null
)
//0
console
.
log
(
+
undefined
)
//Nan
console
.
log
(
+
Infinity
)
//Infinity
console
.
log
(
+
true
)
//1
console
.
log
(
+
false
)
//0
console
.
log
(
+
"0x22"
)
//34
console
.
log
(
+
"0022"
)
//22
console
.
log
(
+
"0o51"
)
//41
console
.
log
(
+
"3.125e7"
)
//31250000
console
.
log
(
+
"35 35"
)
//NaN
console
.
log
(
+
"AB 35"
)
//NaN
|
- Tries to convert any string to a number
-
It converts empty string /
Nullto 0 -
Trueis 1 andFalseis 0 - Converts Octal/Hexa numbers to decimal.
- Works correctly on scientific notation numbers.
-
In case it fails to convert, then returns
NaN
Parseint
The
parseint
function parses an string and returns an integer. The syntax of the
parseInt
is as follows. If you do not provide the
radix
then it assumes the Hexadecimal number.
parseInt(
string, radix
)
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console
.
log
(
parseInt
(
"100"
)
)
//100
console
.
log
(
parseInt
(
"100.5175"
)
)
//100
console
.
log
(
parseInt
(
"10AA0.5175"
)
)
//10
console
.
log
(
parseInt
(
""
)
)
//NaN
console
.
log
(
parseInt
(
null
)
)
//NaN
console
.
log
(
parseInt
(
Infinity
)
)
//NaN
console
.
log
(
parseInt
(
true
)
)
//NaN
console
.
log
(
parseInt
(
false
)
)
//NaN
console
.
log
(
parseInt
(
"0x22"
)
)
//34
console
.
log
(
parseInt
(
"0022"
)
)
//22
console
.
log
(
parseInt
(
"0o51"
)
)
//0
console
.
log
(
parseInt
(
"3.125e7"
)
)
//3
console
.
log
(
parseInt
(
"35 35"
)
)
//35
console
.
log
(
parseInt
(
"AB 35"
)
)
//NaN
|
- Tries to convert any string to a integer and not to floating number
-
Converts empty strings, null, infinity, True & false to a
NaN -
If the string begins with
0xthen it treats it a Hexadecimal number. -
It does not recognize the octal number that begins with
0o -
The older browsers will treat the number starting with
0as Octal. - Ignores the Leading & trailing spaces
- If only the initial part of the string is a number, then it converts into number and ignores the rest.
You can make use of the
radix
. The
radix
can be from 2 to 36. Use
2
for binary,
8
for octal,
10
for decimal &
16
for HexaDecimal number.
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console
.
log
(
parseInt
(
"51"
)
)
;
//51
console
.
log
(
parseInt
(
"51"
,
8
)
)
;
//41
console
.
log
(
parseInt
(
"51"
,
16
)
)
;
//81
console
.
log
(
parseInt
(
"051"
)
)
;
//51
console
.
log
(
parseInt
(
"051"
,
8
)
)
;
//41
console
.
log
(
parseInt
(
"051"
,
16
)
)
;
//81
console
.
log
(
parseInt
(
"0x51"
)
)
;
//81
console
.
log
(
parseInt
(
"0x51"
,
8
)
)
;
//0
console
.
log
(
parseInt
(
"0x51"
,
16
)
)
;
//81
console
.
log
(
parseInt
(
"0o51"
)
)
;
//0
console
.
log
(
parseInt
(
"0o51"
,
8
)
)
;
//0
console
.
log
(
parseInt
(
"0o51"
,
16
)
)
;
//0
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Parsefloat
ParseFloat
is another way to convert string to a number.
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console
.
log
(
parseFloat
(
"100"
)
)
//100
console
.
log
(
parseFloat
(
"100.5175"
)
)
//100.5175
console
.
log
(
parseFloat
(
"10AA0.5175"
)
)
//10
console
.
log
(
parseFloat
(
""
)
)
//NaN
console
.
log
(
parseFloat
(
null
)
)
//NaN
console
.
log
(
parseFloat
(
Infinity
)
)
//Infinity
console
.
log
(
parseFloat
(
true
)
)
//NaN
console
.
log
(
parseFloat
(
false
)
)
//NaN
console
.
log
(
parseFloat
(
"0x22"
)
)
//0
console
.
log
(
parseFloat
(
"0022"
)
)
//22
console
.
log
(
parseFloat
(
"0o51"
)
)
//0
console
.
log
(
parseFloat
(
"3.125e7"
)
)
//31250000
console
.
log
(
parseFloat
(
"35 35"
)
)
//35
console
.
log
(
parseFloat
(
"AB 35"
)
)
//NaN
|
- Tries to convert any string to a decimal or an integer number
-
Converts empty strings, null, True & false to a
NaN - Returns infinity as it is.
- It the string begins with 0x or 0o it returns zero. Does not recognize Hexa decimal or octal numbers
- Ignores the Leading & trailing spaces
- If only the initial part of the string is a number, then it converts into number and ignores the rest.
Number global function
You can also use the
Number
global function. It is very similar to unary plus (
+
)
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console
.
log
(
Number
(
"100"
)
)
//100
console
.
log
(
Number
(
"100.5175"
)
)
//100.5175
console
.
log
(
Number
(
"10AA0.5175"
)
)
//NaN
console
.
log
(
Number
(
""
)
)
//0
console
.
log
(
Number
(
" "
)
)
//0
console
.
log
(
Number
(
null
)
)
//0
console
.
log
(
Number
(
undefined
)
)
//Nan
console
.
log
(
Number
(
Infinity
)
)
//Infinity
console
.
log
(
Number
(
true
)
)
//1
console
.
log
(
Number
(
false
)
)
//0
console
.
log
(
Number
(
"0x22"
)
)
//34
console
.
log
(
Number
(
"0022"
)
)
//22
console
.
log
(
Number
(
"0o51"
)
)
//41
console
.
log
(
Number
(
"3.125e7"
)
)
//31250000
console
.
log
(
Number
(
"35 35"
)
)
//NaN
console
.
log
(
Number
(
"AB 35"
)
)
//NaN
|
- Tries to convert any string to a number
-
It converts empty string /
Nullto 0 -
Trueis 1 andFalseis 0 - Converts Octal/Hexa numbers to decimal.
- Works correctly on scientific notation numbers.
-
In case it fails to convert, then returns
NaN
Check for NaN
The string to number operation may result in a
NaN
. The
NaN
stands for
n
ot
a
n
umber. It is the result of numerical operations, where the result is not a number. Hence always check if the value is
NaN
using the
isNaN
method after the conversion.
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convertToNumber
(
"AB 35"
)
convertToNumber
(
"35"
)
function
convertToNumber
(
numVal
)
{
if
(
isNaN
(
+
numVal
)
)
{
console
.
log
(
"Number is NaN"
)
}
else
{
console
.
log
(
+
numVal
)
}
}
//Output
Number
is
NaN
35
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References
Read More
Checking for NaN is easy in everyday tasks, but so difficult on a code test because there’s so many variable outcomes.