Interface ProgramParameter

A GLenum specifying the information to query. Possible values:

• gl.DELETE_STATUS Returns a GLboolean indicating whether or not the program is flagged for deletion.
• gl.LINK_STATUS Returns a GLboolean indicating whether or not the last link operation was successful.
• gl.VALIDATE_STATUS Returns a GLboolean indicating whether or not the last validation operation was successful.
• gl.ATTACHED_SHADERS Returns a GLint indicating the number of attached shaders to a program.
• gl.ACTIVE_ATTRIBUTES Returns a GLint indicating the number of active attribute variables to a program.
• gl.ACTIVE_UNIFORMS Returns a GLint indicating the number of active uniform variables to a program.

When using a WebGL 2 context, the following values are available additionally:

• gl.TRANSFORM_FEEDBACK_BUFFER_MODE Returns a GLenum indicating the buffer mode when transform feedback is active. May be gl.SEPARATE_ATTRIBS or gl.INTERLEAVED_ATTRIBS.
• gl.TRANSFORM_FEEDBACK_VARYINGS Returns a GLint indicating the number of varying variables to capture in transform feedback mode.
• gl.ACTIVE_UNIFORM_BLOCKS Returns a GLint indicating the number of uniform blocks containing active uniforms.

See

https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/getProgramParameter