k8s-set-context/node_modules/xpath/docs/variable resolvers.md

Variable Resolvers

The methods on the XPathEvaluator type can optionally take a variable resolver to resolve variable references in the XPath expression being evaluated.

There are three ways to specify a variable resolver and you can use any one of them depending on which is most suited to your particular situation.

Note that if your variables are in a namespace (e.g. $myVars:var), you must use the second or third type as the plain object implementation does not support namespaces.

Variable values

You can use any of five types of values to specify the values of variables:

• string
• number
• boolean
• single node (will be treated as a node set)
• array of nodes or array-like collection of nodes (will be treated as a node set)

Variable Resolver Type 1: Plain object

A plain object with variable names as the keys and variable values as the values.

Example usage:

var evaluator = xpath.parse('concat($character1, ", ", $character2, ", and ", $character3)');
var mainCharacters = evaluator.evaluateString({
	variables: {
		character1: 'Harry',
        character2: 'Ron',
        character3: 'Hermione'
	}
});

Variable Resolver Type 2: Function

A function that takes a variable name as its first parameter and an optional namespace URI as its second parameter and returns a value based on the name and namespace.

Example usage:

var evaluator = xpath.parse('concat($hp:character1, ", ", $hp:character2, ", and ", $hp:character3)');
var mainCharacters = evaluator.evaluateString({
	variables: function (name, namespace) {
        if (namespace === 'http://sample.org/harrypotter/') {
            switch (name) {
                case 'character1': return 'Harry';
                case 'character2': return 'Ron';
                case 'character3': return 'Hermione';
            }
        }
	},
    namespaces: {
        hp: 'http://sample.org/harrypotter/'
    }
});

Function Resolver Type 3: Object with getFunction method

An object with a method named getVariable that works in the same way as the function-based variable resolver described above.

Example usage:

var evaluator = xpath.parse('concat($hp:character1, ", ", $hp:character2, ", and ", $hp:character3)');
var mainCharacters = evaluator.evaluateString({
	variables: {
        getVariable: function (name, namespace) {
            if (namespace === 'http://sample.org/harrypotter/') {
                switch (name) {
                    case 'character1': return 'Harry';
                    case 'character2': return 'Ron';
                    case 'character3': return 'Hermione';
                }
            }
	    }
    },
    namespaces: {
        hp: 'http://sample.org/harrypotter/'
    }
});