Function safeFieldName

packages/sanddance-specs/src/expr.ts:9–11

(field: string)

 * examples: "source.x", "target['x']", "[my.field]"
 */
export function safeFieldName(field: string) {
    return field.replace('.', '\\.').replace('[', '\\[').replace(']', '\\]');
}

/**
 * Make sure the field name is usable in a Vega expression