JavaScript equivalent of Python's format() function?

Question

Python has this beautiful function to turn this:

bar1 = \'foobar\'
bar2 = \'jumped\'
bar3 = \'dog\'

foo = \'The lazy \' + bar3 + \' \' + bar2 \' over the \'         


        

Answer 1

For those looking for a simple ES6 solution.

First of all I'm providing a function instead of extending native String prototype because it is generally discouraged.

// format function using replace() and recursion

const format = (str, arr) => arr.length > 1 
	? format(str.replace('{}', arr[0]), arr.slice(1)) 
	: (arr[0] && str.replace('{}', arr[0])) || str

// Example usage

const str1 = 'The {} brown {} jumps over the {} dog'

const formattedString = formatFn(str1, ['quick','fox','lazy'])

console.log(formattedString)

Answer 2

You can use template literals in JS,

const bar1 = 'foobar'
const bar2 = 'jumped'
const bar3 = 'dog'
foo = `The lazy ${bar3} ${bar2} over the ${bar1}`

I think this was helpful.

Answer 3

Usando split:

String.prototype.format = function (args) {
    var text = this
    for(var attr in args){
        text = text.split('${' + attr + '}').join(args[attr]);
    }
    return text
};

json = {'who':'Gendry', 'what':'will sit', 'where':'in the Iron Throne'}
text = 'GOT: ${who} ${what} ${where}';

console.log('context: ',json);
console.log('template: ',text);
console.log('formated: ',text.format(json));

Usando Regex:

String.prototype.format = function (args) {
    var text = this
    for(var attr in args){
        var rgx = new RegExp('${' + attr + '}','g');
        text = text.replace(rgx, args[attr]);
    }
    return text
};

json = {'who':'Gendry', 'what':'will sit', 'where':'in the Iron Throne'}
text = 'GOT: ${who} ${what} ${where}';

console.log('context: ',json);
console.log('template: ',text);
console.log('formated: ',text.format(json));

Answer 4

In the file

https://github.com/BruceSherwood/glowscript/blob/master/lib/glow/api_misc.js

is a function String.prototype.format = function(args) that fully implements the Python string.format() function, not limited simply to handling character strings.

Answer 5

My own srtipped down version of YAHOO's printf reported by PatrikAkerstrand:

function format() { 
  return [...arguments].reduce((acc, arg, idx) => 
    acc.replace(new RegExp("\\{" + (idx - 1) + "\\}", "g"), arg));
}

console.log(
  format('Confirm {1} want {0} beers', 3, 'you')
);