jsonPlaceholderReplacer

Lightweight yet really powerful typescript library/cli to replace placeholders in an javascript object/JSON. By default, all you have to do is to use double curly brackets {{placeholderKey}} or angle brackets <<placeholderKey>>, interchangeably, to identify the placeholder. Don't worry, if you don't like these default placeholders you can create your own.

CLI usage

json-placeholder-replacer annotetad-json.json [...variableMaps]

Example

$ json-placeholder-replacer annotated.json variable_map.json $ jpr variable_map.json < annotated.json $ cat annotated.json | jpr variable_map.json $ echo '{"curly": "{{key}}", "angle": "<>"}' | jpr variable_maps

Would result

cat replaceable.json
        # {
        #  "curly": "{{key}}",
        #  "angle": "<<key>>"
        # }
cat variable.map:
        # {
        #         "key": 10,
        #         "not-mapped": 20
        # }
json-placeholder-replacer replaceable.json variable.map
        # {
        #         "curly": 10,
        #         "angle": 10,
        #         "not-mapped": 20
        # }

Library usage

import { JsonPlaceholderReplacer } from "json-placeholder-replacer";
const placeHolderReplacer = new JsonPlaceholderReplacer();

placeHolderReplacer.addVariableMap({
  key: 100,
  otherKey: 200,
});
const afterReplace = placeHolderReplacer.replace({
  replaceable: "{{key}}",
  otherReplaceableWithSameKey: "<<key>>",
  otherReplaceable: "{{otherKey}}",
});

// afterReplace = {
//    replaceable: 100,
//    otherReplaceableWithSameKey: 100,
//    otherReplaceable: 200
// }

Note

An object passed to .replace() is mutated in-place:

const beforeReplace = { some: "{{placeholder}}" };
const afterReplace = placeHolderReplacer.replace(beforeReplace);
// beforeReplace === afterReplace

You can replace the default placeholders with some as cool as you want

const placeHolderReplacer = new JsonPlaceholderReplacer({
  delimiterTags: [{ begin: "@{{-", end: "-}}@" }],
});
placeHolderReplacer.addVariableMap({
  key: "nice",
});
const afterReplace = placeHolderReplacer.replace({
  replaceable: "@{{-key-}}@",
});

// afterReplace = {
//    replaceable: "nice",
// }

It's also possible to add more than one variables map

placeHolderReplacer.addVariableMap({
  firstMapKey: "1",
});
placeHolderReplacer.addVariableMap({
  secondMapKey: 2,
});
const afterReplace = placeHolderReplacer.replace({
  replaceable: "{{firstMapKey}}",
  otherReplaceable: "<<secondMapKey>>",
});

// afterReplace = {
//    replaceable: "1",
//    otherReplaceable: 2
// }

And the last added maps have higher priority (but non-nullish values will be preserved from previous map)

placeHolderReplacer.addVariableMap({
  id: "lowerPriority",
  name: "Name",
});
placeHolderReplacer.addVariableMap({
  id: "higherPriority",
  name: undefined,
});
const afterReplace = placeHolderReplacer.replace({
  id: "{{id}}",
  name: "{{name}}",
});

// afterReplace = {
//    id: "higherPriority"
//    name: "Name"
// }

It's possible to override global values map with .setVariableMap()

placeHolderReplacer.addVariableMap({
  id: "Id",
  name: "Name",
});
placeHolderReplacer.setVariableMap({
  // <- note setVariableMap() here
  id: "New Id",
  name: undefined,
});
const afterReplace = placeHolderReplacer.replace({
  id: "{{id}}",
  name: "{{name}}",
});

// afterReplace = {
//    id: "New Id"
//    name: "{{name}}"
// }

It's possible to override global maps with local by .replaceWith()

placeHolderReplacer.addVariableMap({
  id: "Id",
  name: "Name",
});
const afterReplace = placeHolderReplacer.replaceWith(
  {
    id: "{{id}}",
    name: "{{name}}",
  },
  { name: "New Name" },
);

// afterReplace = {
//    id: "{{id}}"
//    name: "New Name"
// }

It keeps original variable types

If a variable in the map is boolean/string/number/object, it remains as boolean/string/number/object when it's replaced

placeHolderReplacer.addVariableMap({
  booleanKey: true,
  stringKey: "string",
  numberKey: 10,
  objectKey: {
    inner: "inner",
  },
});
const afterReplace = placeHolderReplacer.replace({
  booleanReplaceable: "{{booleanKey}}",
  stringReplaceable: "{{stringKey}}",
  numberReplaceable: "{{numberKey}}",
  objectReplaceable: "{{objectKey}}",
});

// afterReplace = {
//    booleanReplaceable: true,
//    stringReplaceable: "string",
//    numberReplaceable: 10,
//    objectReplaceable: {
//      inner: "inner"
//    }
// }

Just to make it clearer, it does not replace the placeholder Key

placeHolderReplacer.addVariableMap({
  key: "someValue",
});
const afterReplace = placeHolderReplacer.replace({
  "{{key}}": "value",
});
// afterReplace = {
//    "{{key}}": "value"
// }

And, of course, it handles array substitution as well

placeHolderReplacer.addVariableMap({
  key: 987,
  objectReplaceable: {
    inner: "inner",
  },
});
const afterReplace = placeHolderReplacer.replace({
  array: ["string", "{{objectReplaceable}}", "{{key}}"],
});

// afterReplace = {
//    array: ["string", { inner: "inner" }, 987]
// }

Want to get nested elements? Go for it

placeHolderReplacer.addVariableMap({
  key: {
    nested: "value",
  },
});
const afterReplace: any = placeHolderReplacer.replace({
  replaceable: "<<key.nested>>",
});

// afterReplace = {
//    replaceable: "value"
// }

This feature allows you to have default values in case you don't have them mapped

placeHolderReplacer.addVariableMap({
  key: "value",
});
const afterReplace: any = placeHolderReplacer.replace({
  replaceable: "<<not-found-key:default-value>>",
});

// afterReplace = {
//    replaceable: "default-value"
// }

Of course, you can also change what is the default value separator (defaults to ':')

const placeHolderReplacer = new JsonPlaceholderReplacer({
  defaultValueSeparator: ":=:",
});

placeHolderReplacer.addVariableMap({
  key: "value",
});
const afterReplace: any = placeHolderReplacer.replace({
  replaceable: "<<not-found-key:=:default-value>>", // Note the ':=:'
});

// afterReplace = {
//    replaceable: "default-value"
// }