String.Format
does not work in TypeScript
.
Error:
The property 'format' does not exist on value of type '{ prototype: String; fromCharCode(...codes: number[]): string; (value?: any): string; new(value?: any): String; }'.
attributes["Title"] = String.format(
Settings.labelKeyValuePhraseCollection["[WAIT DAYS]"],
originalAttributes.Days
);
TypeScript doesn't add to the native objects, so it also doesn't have a String. format function. You can then use the feature: var myStr = 'This is an {0} for {0} purposes: {1}'; alert(myStr.
JavaScript's String type is used to represent textual data. It is a set of "elements" of 16-bit unsigned integer values (UTF-16 code units). Each element in the String occupies a position in the String. The first element is at index 0, the next at index 1, and so on.
Use the String() object to convert a number to a string in TypeScript, e.g. const str = String(num) . When used as a function, the String object converts the passed in value to a primitive string and returns the result. Copied!
String interpolation is a great programming language feature that allows injecting variables, function calls, arithmetic expressions directly into a string. String interpolation was absent in JavaScript before ES6.
You can use TypeScript's native string interpolation in case if your only goal to eliminate ugly string concatenations and boring string conversions:
var yourMessage = `Your text ${yourVariable} your text continued ${yourExpression} and so on.`
NOTE:
At the right side of the assignment statement the delimiters are neither single or double quotes, instead a special char called backtick or grave accent.
The TypeScript compiler will translate your right side special literal to a string concatenation expression. With other words this syntax does not rely on the ECMAScript 6 feature, instead a native TypeScript feature. Your generated javascript code remains compatible.
Note: As of TypeScript 1.4, string interpolation is available in TypeScript:
var a = "Hello";
var b = "World";
var text = `${a} ${b}`
This will compile to:
var a = "Hello";
var b = "World";
var text = a + " " + b;
The JavaScript String
object doesn't have a format
function. TypeScript doesn't add to the native objects, so it also doesn't have a String.format
function.
For TypeScript, you need to extend the String interface and then you need to supply an implementation:
interface String {
format(...replacements: string[]): string;
}
if (!String.prototype.format) {
String.prototype.format = function() {
var args = arguments;
return this.replace(/{(\d+)}/g, function(match, number) {
return typeof args[number] != 'undefined'
? args[number]
: match
;
});
};
}
You can then use the feature:
var myStr = 'This is an {0} for {0} purposes: {1}';
alert(myStr.format('example', 'end'));
You could also consider string interpolation (a feature of Template Strings), which is an ECMAScript 6 feature - although to use it for the String.format
use case, you would still need to wrap it in a function in order to supply a raw string containing the format and then positional arguments. It is more typically used inline with the variables that are being interpolated, so you'd need to map using arguments to make it work for this use case.
For example, format strings are normally defined to be used later... which doesn't work:
// Works
var myFormatString = 'This is an {0} for {0} purposes: {1}';
// Compiler warnings (a and b not yet defines)
var myTemplateString = `This is an ${a} for ${a} purposes: ${b}`;
So to use string interpolation, rather than a format string, you would need to use:
function myTemplate(a: string, b: string) {
var myTemplateString = `This is an ${a} for ${a} purposes: ${b}`;
}
alert(myTemplate('example', 'end'));
The other common use case for format strings is that they are used as a resource that is shared. I haven't yet discovered a way to load a template string from a data source without using eval
.
I solved it like this;
1.Created a function
export function FormatString(str: string, ...val: string[]) {
for (let index = 0; index < val.length; index++) {
str = str.replace(`{${index}}`, val[index]);
}
return str;
}
2.Used it like the following;
FormatString("{0} is {1} {2}", "This", "formatting", "hack");
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