# nlohmann::json_pointer::push_front

```
void push_front(const string_t& token);

void push_front(string_t&& token);
```

Append an unescaped token at the start of the reference pointer.

## Parameters

`token` (in) : token to add

## Exception safety

Basic guarantee: if an exception is thrown (for instance, if copying the reference token fails), the JSON pointer is left in a valid state, but its reference tokens may have changed.

## Complexity

Linear in the number of reference tokens in the `json_pointer`.

## Examples

Example

The example shows the result of `push_front` for different JSON Pointers.

```
#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;

int main()
{
    // create empty JSON Pointer
    json::json_pointer ptr;
    std::cout << "\"" << ptr << "\"\n";

    // call push_front()
    ptr.push_front("foo");
    std::cout << "\"" << ptr << "\"\n";

    ptr.push_front("0");
    std::cout << "\"" << ptr << "\"\n";

    ptr.push_front("bar");
    std::cout << "\"" << ptr << "\"\n";
}
```

Output:

```
""
"/foo"
"/0/foo"
"/bar/0/foo"
```

## See also

- [front](https://json.nlohmann.me/api/json_pointer/front/index.md) return first reference token
- [pop_front](https://json.nlohmann.me/api/json_pointer/pop_front/index.md) remove the first reference token

## Version history

- Added in version 3.13.0 unreleased.