Object path - misonou/waterpipe GitHub Wiki

The basic construct consist of an object path in a double-braced expression {{path}} where path is basically Javascript's dot notation (.) except that array indices are also accepted.

Consider the following input object:

{ zero: 0, string: "foo", array: [1, 2, 3, 4] }

The following object path will be interpolated as:

{{string}} ➜ foo
{{array}} ➜ [1,2,3,4]
{{array.0}} ➜ 1
{{array.length}} ➜ 4

In addition, any parts of the object path can be itself evaluated by a preceding dollar sign ($).

{{array.$zero}} = {{array.0}} ➜ 1
{{array.$(array.0)}} = {{array.1}} ➜ 2

When interpolating, it is short-circuited if at any step it evaluates to undefined or null. It is commonly equivalent to the ?. operator by other languages or template engines:

{{blah}} ➜
{{array.foo.bar}} ➜ 

Invalid path has a stricter sense then nonexistent path that, the first part of the object path does not exist as a property on all visible objects in the interpolation context.

Referencing the example in the previous section, {{array.foo.bar}} is a nonexistent path, while {{blah}} is an invalid path.

Special handling is done on invalid path when executing the pipe. See Pipe for more information.

Waterpipe supports declaring global variables. See Global variables for more details.

// the following returns the string "foobar"
// even though `myGlobal` is not found on the input data object
waterpipe('{{myGlobal}}', { /* no properties */ }, {
    globals: {
        myGlobal: 'foobar'
    }
});