gecko/xpcom/analysis/string-format.js

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String.prototype.format = function string_format() {
// there are two modes of operation... unnamed indices are read in order;
// named indices using %(name)s. The two styles cannot be mixed.
// Unnamed indices can be passed as either a single argument to this function,
// multiple arguments to this function, or as a single array argument
let curindex = 0;
let d;
if (arguments.length > 1) {
d = arguments;
}
else
d = arguments[0];
function r(s, key, type) {
let v;
if (key == "") {
if (curindex == -1)
throw Error("Cannot mix named and positional indices in string formatting.");
if (curindex == 0 && (!(d instanceof Object) || !(0 in d))) {
v = d;
}
else if (!(curindex in d))
throw Error("Insufficient number of items in format, requesting item %i".format(curindex));
else {
v = d[curindex];
}
++curindex;
}
else {
key = key.slice(1, -1);
if (curindex > 0)
throw Error("Cannot mix named and positional indices in string formatting.");
curindex = -1;
if (!(key in d))
throw Error("Key '%s' not present during string substitution.".format(key));
v = d[key];
}
switch (type) {
case "s":
if (v === undefined)
return "<undefined>";
return v.toString();
case "r":
return uneval(v);
case "i":
return parseInt(v);
case "f":
return Number(v);
case "%":
return "%";
default:
throw Error("Unexpected format character '%s'.".format(type));
}
}
return this.replace(/%(\([^)]+\))?(.)/g, r);
};